Add Blockly messages to playground

playground/index.html

@@ -445,6 +445,7 @@
     <script src="../node_modules/scratch-blocks/blockly_compressed_vertical.js"></script>
     <script src="../node_modules/scratch-blocks/blocks_compressed.js"></script>
     <script src="../node_modules/scratch-blocks/blocks_compressed_vertical.js"></script>
+    <script src="../node_modules/scratch-blocks/msg/messages.js"></script>
     <!-- Renderer -->
     <script src="../node_modules/scratch-render-webgl/build/render-webgl.js"></script>
     <!-- VM Worker -->