Fix entry problem

Author: pgaultier

sample-app/webpack-yii2.json

@@ -1,6 +1,8 @@
 {
     "sourceDir": "protected\/assets\/webpack",
-    "entry": {},
+    "entry": {
+        "app": "./app.ts"
+    },
     "commonBundles": [
         "manifest"
     ],
@@ -13,4 +15,4 @@
         "scripts": "js"
     },
     "catalog": "assets-catalog.json"
-}
+}