Added build scripts

.gitignore

 node_modules/
 private-tests/
+dist/

bin/fixup.sh

+#!/bin/sh
+cat >$(pwd)/dist/cjs/package.json <<!EOF
+{
+    "type": "commonjs"
+}
+!EOF
+
+cat >$(pwd)/dist/esm/package.json <<!EOF
+{
+    "type": "module"
+}
+!EOF

package.json

@@ -2,9 +2,21 @@
   "name": "bip47-js",
   "version": "0.4.0",
   "description": "A set of utilities for working with BIP47 and bitcoinjs-lib",
-  "main": "src/index.js",
+  "main": "dist/cjs/index.js",
+  "module": "dist/esm/index.js",
+  "exports": {
+    ".": {
+      "import": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js"
+    }
+  },
   "scripts": {
-    "test": "mocha --recursive --reporter spec"
+    "test": "mocha -r ts-node/register test/**/*.ts",
+    "typescript": "tsc --noEmit",
+    "build:clean": "rm -rf dist",
+    "build:cjs": "tsc -p tsconfig.build.cjs.json",
+    "build:esm": "tsc -p tsconfig.build.esm.json",
+    "build": "npm run build:clean && npm run build:cjs && npm run build:esm && bin/fixup.sh"
   },
   "repository": {
     "type": "git",

tsconfig.build.cjs.json

+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "target": "ES2015",
+    "module": "commonjs",
+    "rootDir": "./src",
+    "outDir": "./dist/cjs"
+  },
+  "exclude": [
+    "test"
+  ]
+}

tsconfig.build.esm.json

+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ES2020",
+    "rootDir": "./src",
+    "outDir": "./dist/esm"
+  },
+  "exclude": [
+    "test"
+  ]
+}

tsconfig.json

+{
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig.json to read more about this file */
+
+    /* Basic Options */
+    // "incremental": true,                         /* Enable incremental compilation */
+    "target": "es2020",                             /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
+    "module": "commonjs",                           /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
+    // "lib": [],                                   /* Specify library files to be included in the compilation. */
+    "allowJs": true,                                /* Allow javascript files to be compiled. */
+    // "checkJs": true,                             /* Report errors in .js files. */
+    // "jsx": "preserve",                           /* Specify JSX code generation: 'preserve', 'react-native', 'react', 'react-jsx' or 'react-jsxdev'. */
+    "declaration": true,                            /* Generates corresponding '.d.ts' file. */
+    "declarationMap": true,                         /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    "sourceMap": true,                              /* Generates corresponding '.map' file. */
+    // "outFile": "./",                             /* Concatenate and emit output to single file. */
+    // "outDir": "./dist",                          /* Redirect output structure to the directory. */
+    "rootDir": ".",                                 /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                           /* Enable project compilation */
+    // "tsBuildInfoFile": "./",                     /* Specify file to store incremental compilation information */
+    "removeComments": true,                         /* Do not emit comments to output. */
+    // "noEmit": true,                              /* Do not emit outputs. */
+    // "importHelpers": true,                       /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,                  /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    "isolatedModules": true,                        /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+    "noEmitOnError": true,
+
+    /* Strict Type-Checking Options */
+    "strict": true,                                 /* Enable all strict type-checking options. */
+    // "noImplicitAny": true,                       /* Raise error on expressions and declarations with an implied 'any' type. */
+    // "strictNullChecks": true,                    /* Enable strict null checks. */
+    // "strictFunctionTypes": true,                 /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,                 /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "strictPropertyInitialization": true,        /* Enable strict checking of property initialization in classes. */
+    "noImplicitThis": true,                         /* Raise error on 'this' expressions with an implied 'any' type. */
+    "alwaysStrict": true,                           /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                      /* Report errors on unused locals. */
+    // "noUnusedParameters": true,                  /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,                   /* Report error when not all code paths in function return a value. */
+    "noFallthroughCasesInSwitch": true,             /* Report errors for fallthrough cases in switch statement. */
+    // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
+    // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+
+    /* Module Resolution Options */
+    "moduleResolution": "node",                     /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "",                               /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                                 /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                              /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                             /* List of folders to include type definitions from. */
+    // "types": [],                                 /* Type declaration files to be included in compilation. */
+    "allowSyntheticDefaultImports": true,        /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true,                        /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,                    /* Do not resolve the real path of symlinks. */
+    // "allowUmdGlobalAccess": true,                /* Allow accessing UMD globals from modules. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                            /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                               /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,                     /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                       /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    // "experimentalDecorators": true,              /* Enables experimental support for ES7 decorators. */
+    // "emitDecoratorMetadata": true,               /* Enables experimental support for emitting type metadata for decorators. */
+
+    /* Advanced Options */
+    "skipLibCheck": true,                           /* Skip type checking of declaration files. */
+    "forceConsistentCasingInFileNames": true        /* Disallow inconsistently-cased references to the same file. */
+  },
+  "exclude": [
+    "node_modules",
+    "dist",
+  ],
+  "include": [
+    "src/**/*.ts",
+    "test/**/*.ts"
+  ]
+}