build Dual CommonJS/ES module package

[semmel]

Use ES module loader in browser, Node and bundlers – e.g.

• import {Maybe} from 'purify-ts/Maybe.js'
• import {Maybe} from 'purify-ts/Maybe' (requires import-map in browsers)
• import("purify-ts/Maybe").then(m => { globalThis.Maybe = m.Maybe; });
• use rollup with plugin @rollup/plugin-node-resolve
• follows Node.js' docs for Dual CommonJS/ES module packages

CommonJS support should be untouched

node -e 'const Maybe = require("purify-ts").Maybe; console.log(Maybe.of("foo").orDefault("bar"));'
--> "foo"

Two additional dev-dependencies

Unfortunately the TypeScript compiler still generates bare import specifiers in the js files. Many ways to "Provide a way to add the '.js' file extension to the end of module specifiers" are available to the JS community.

I choose the compiler plugin because both dependencies are themselves dependency-free – so less of a hassle to keep them up-to-date.

[gigobyte]

Published 1.3.0-rc1 and tested the output with commonjs, mjs and tsc - all work!

Thanks for the contribution!