fix(builds): point jsnext:main to the ESM build instead of src, which contains things like Flowtype annotations that are not stripped by most build tools

Author: developit

package.json

@@ -2,7 +2,7 @@
   "name": "mitt",
   "version": "1.1.1",
   "description": "Tiny 200b functional Event Emitter / pubsub.",
-  "jsnext:main": "src/index.js",
+  "jsnext:main": "dist/mitt.es.js",
   "module": "dist/mitt.es.js",
   "main": "dist/mitt.js",
   "umd:main": "dist/mitt.umd.js",