chore: Use bili bundler.

[hastebrot]

This replaces Webpack with Bili (a bundler based on Rollup).

Main reason is that I want to use tcomb on ObservableHQ (for notebook-based programming) via unpkg.com. It currently only includes CommonJS bundles and the dist/ directory is missing: (see: https://unpkg.com/tcomb@3.2.29/).

I've added/modified entries in package.json (which seems a sane default) to let unpkg.com and jsdelivr.com know where to find the bundles. Adapted from https://github.com/immerjs/immer/blob/v3.1.1/package.json. The umd:main output is minified for use in browsers.

{
  "main": "dist/tcomb.js",
  "module": "dist/tcomb.module.js",
  "umd:main": "dist/tcomb.umd.js",
}

It adds a bili.config.ts where you can e.g. configure the formats. The apidocs (https://bili.egoist.sh/api/globals.html#format) say you can additionally use "cjs-min" | "es-min" | "esm-min" | "umd-min" | "iife-min" | "amd-min" | "system-min". Adapted from https://github.com/immerjs/immer/blob/v3.1.1/bili.config.ts.

import { Config } from "bili";

const config: Config = {
  input: {
    tcomb: "index.js"
  },
  output: {
    format: ["cjs", "umd", "esm"],
    moduleName: "tcomb",
    sourceMap: true,
    sourceMapExcludeSources: true
  },

Finally I've changed package.json scripts to have build and test. I think unpkg.com needs it to process the bundles and put it into dist/ for each release. I've run npm run build and npm run test and it works. Do we want to add both steps to .travis.yml?

  "scripts": {
    "build": "rimraf dist/ && bili",
    "test": "npm run lint && mocha && npm run typescript && npm run perf",
    "lint": "eslint index.js lib test",
    "perf": "node ./perf/perf",
    "typescript": "tsc --noEmit tcomb-tests.ts"
  },

I've also tested microbundle but Bili was better documented and configurable. Not relevant for tcomb bundle process but worth mentioning: It also does not leave annoying build cache directories used by rollup-plugin-typescript2 (this can be also configured). Also iife output option is documented and does not clash with cjs output configuration like in microbundle. Bili is much smaller than microbundle (see "Bili vs Microbundle" issue at egoist/bili#163).

• Bili repository: https://github.com/egoist/bili
• Bili documentation: https://bili.egoist.sh/#/

[hastebrot]

I guess main in package.json has to be changed back to index.js (from dist/tcomb.js), since we are not running npm run build on every npm publish.

[hastebrot]

Done. This is good for review now.

[hastebrot]

So, probably we want to have tcomb.js for development and tcomb.min.js for production (see: https://github.com/gcanti/tcomb/tree/v3.2.29#how-to-build-a-standalone-bundle).

[hastebrot]

I think we can decrease the bundle size more. Seems Webpack creates smaller bundles than Bili.