Addind external support

Author: pgaultier

sample-app/webpack-yii2.json

@@ -6,6 +6,9 @@
     "commonBundles": [
         "manifest"
     ],
+    "externals": {
+
+    },
     "subDirectories": {
         "sources": "src",
         "dist": "dist"

sample-app/webpack.config.js

@@ -76,6 +76,7 @@ module.exports = {
             }
         })
     ],
+    externals: config.externals,
     module: {
         rules: [
             {