fix: use module field for es6 build (#105)

Author: pravdomil

package.json

@@ -2,7 +2,8 @@
   "name": "react-popper",
   "version": "0.8.2",
   "description": "React wrapper around PopperJS.",
-  "main": "lib/react-popper.js",
+  "main": "dist/react-popper.js",
+  "module": "lib/react-popper.js",
   "types": "react-popper.d.ts",
   "files": [
     "dist",