build: remove process.env.NODE_ENV in UMD build

Currently it was included in the minified UMD bundle, making it impossible to use it in the browser.

Author: thebuilder

rollup.config.js

@@ -3,6 +3,7 @@ import path from 'path'
 import babel from 'rollup-plugin-babel'
 import resolve from 'rollup-plugin-node-resolve'
 import commonjs from 'rollup-plugin-commonjs'
+import replace from 'rollup-plugin-replace'
 import { uglify } from 'rollup-plugin-uglify'
 import pkg from './package.json'
 
@@ -49,6 +50,7 @@ export default [
         external: Object.keys(globals),
         plugins: [
           resolve(),
+          replace({ 'process.env.NODE_ENV': JSON.stringify('production') }),
           babel(getBabelOptions({ useESModules: true })),
           commonjs({ include: '**/node_modules/**' }),
           uglify(),