fix: Add some code splitting for PWA build (#937)

* fix: Add some code splitting for PWA build

* Fix missing files

extensions/vtk/.webpack/webpack.prod.js

@@ -1,3 +1,4 @@
+const webpack = require('webpack');
 const merge = require('webpack-merge');
 const path = require('path');
 const webpackCommon = require('./../../../.webpack/webpack.commonjs.js');
@@ -34,5 +35,10 @@ module.exports = (env, argv) => {
       libraryExport: 'default',
       filename: pkg.main,
     },
+    plugins: [
+      new webpack.optimize.LimitChunkCountPlugin({
+        maxChunks: 1,
+      }),
+    ],
   });
 };