fix: remove browser field with umd bundle (#541)

The `browser` field has a priority over `module` field in all bundlers. Adding it to package.json drops all goodness of esm bundle.

Author: TrySound

package.json

@@ -11,7 +11,6 @@
   "source": "src/index.js",
   "main": "dist/react-sortable-hoc.js",
   "umd:main": "dist/react-sortable-hoc.umd.js",
-  "browser": "dist/react-sortable-hoc.umd.js",
   "module": "dist/react-sortable-hoc.esm.js",
   "jsnext:main": "dist/react-sortable-hoc.esm.js",
   "types": "types/index.d.ts",