Add ES-browser build (#3143)

* Add ES-browser build

This build is intended for users who want to use Redux
in a browser with ES modules support. The build removes
all references to `process` by assuming it is in a
production environment.

Additionally, it does not transpile, as all browsers
that have ES modules support also support ES2015+

* Build browser-compatible package in es folder

* Remove unnecessary whitespace

* Minify browser build

* Rename to just redux.mjs

Author: TimvdLippe

package-lock.json

@@ -28,6 +28,26 @@ export default [
       babel()
     ]
   },
+  {
+    input: 'src/index.js',
+    output: { file: 'es/redux.mjs', format: 'es', indent: false },
+    plugins: [
+      nodeResolve({
+        jsnext: true
+      }),
+      replace({
+        'process.env.NODE_ENV': JSON.stringify('production')
+      }),
+      terser({
+        compress: {
+          pure_getters: true,
+          unsafe: true,
+          unsafe_comps: true,
+          warnings: false
+        }
+      })
+    ]
+  },
   {
     input: 'src/index.js',
     output: {