feat(*): allow bundler to optimize filesize

The library is side effect free and it should hint this to
all common bundler like rollup, webpack and parcel, so
that they can easily optimize for that.

See: https://webpack.js.org/guides/tree-shaking/

package.json

@@ -5,6 +5,7 @@
   "main": "dist/index.js",
   "module": "dist/index.es.js",
   "types": "dist/index.d.ts",
+  "sideEffects": false,
   "scripts": {
     "start": "rm -rf ./.cache && parcel ./examples/index.html --out-dir='examples-dist'",
     "precompile": "rm -rf dist",