Add native ESM support

Author: wojtekmaj

package.json

@@ -6,6 +6,10 @@
   "module": "dist/esm/index.js",
   "source": "src/index.js",
   "sideEffects": false,
+  "type": "module",
+  "exports": {
+    "default": "./dist/esm/index.js"
+  },
   "scripts": {
     "build": "yarn build-esm && yarn build-umd",
     "build-esm": "BABEL_ENV=production-esm babel src -d dist/esm --ignore **/*.spec.js",