chore: migrate to rollup

This change allows us to:

- reduce the size of the bundle
- provide an ESM bundle (for usage in <script type="module">)

Related: #1198

lib/browser-entrypoint.ts

@@ -0,0 +1,3 @@
+import { io } from "./index.js";
+
+export default io;

package.json

@@ -41,6 +41,10 @@
     "@babel/core": "^7.15.0",
     "@babel/plugin-transform-object-assign": "^7.14.5",
     "@babel/preset-env": "^7.15.0",
+    "@rollup/plugin-alias": "^3.1.5",
+    "@rollup/plugin-babel": "^5.3.0",
+    "@rollup/plugin-commonjs": "^21.0.0",
+    "@rollup/plugin-node-resolve": "^13.0.5",
     "@sinonjs/fake-timers": "^7.1.2",
     "@types/mocha": "^9.0.0",
     "@types/node": "^16.7.6",
@@ -55,6 +59,8 @@
     "mocha": "^3.3.0",
     "prettier": "^2.3.2",
     "rimraf": "^3.0.2",
+    "rollup": "^2.58.0",
+    "rollup-plugin-terser": "^7.0.2",
     "socket.io": "3.0.0",
     "socket.io-browsers": "^1.0.0",
     "socket.io-msgpack-parser": "^3.0.0",
@@ -76,7 +82,7 @@
     "test:node": "mocha --require ts-node/register --reporter dot --require test/support/server.js test/index.js",
     "test:browser": "zuul test/index.js",
     "test:types": "tsd",
-    "build": "npm run compile && webpack --config ./support/webpack.config.js --config ./support/prod.config.js --config ./support/msgpack-parser.config.js",
+    "build": "rollup -c support/rollup.config.umd.js && rollup -c support/rollup.config.esm.js && rollup -c support/rollup.config.umd.msgpack.js",
     "format:check": "prettier --check \"lib/**/*.ts\" \"test/**/*.js\" \"test/**/*.ts\" \"support/**/*.js\"",
     "format:fix": "prettier --write \"lib/**/*.ts\" \"test/**/*.js\" \"test/**/*.ts\" \"support/**/*.js\"",
     "prepack": "npm run compile"