Fixes #1947 Fix webpack reordering import statements

@here/generator-harp.gl/generators/app/templates/javascript/decoder.js

@@ -4,8 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-self.importScripts("three.min.js");
-
+import "./deps";
 import {
     GeoJsonTilerService,
     VectorTileDecoderService

@here/generator-harp.gl/generators/app/templates/javascript/deps.js

@@ -0,0 +1,8 @@
+/*
+ * Copyright (C) 2017-2020 HERE Europe B.V.
+ * Licensed under Apache 2.0, see full license in LICENSE
+ * SPDX-License-Identifier: Apache-2.0
+ */
+// This file is a simple work for webpack reordering the dependencies, i.e. imports are put
+// before importScripts.
+self.importScripts("three.min.js");