v2 Enable local development (#52)

- Create local dev environment
- Add gas-client and google-apps-script-webpack-dev-server packages for development
- Add dev/ wrapper app
- Update webpack config to support development environment
- Redesigned READMEs
- Support typescript
- Update npm scripts
- Organize and update .gitignore file
- Add .vscode settings for clasp files
- Remove tracking for files in dist/

src/server/ui.js

@@ -1,10 +1,11 @@
 export const onOpen = () => {
-  SpreadsheetApp.getUi()
+  const menu = SpreadsheetApp.getUi()
     .createMenu('My Sample React Project') // edit me!
     .addItem('Sheet Editor', 'openDialog')
     .addItem('Sheet Editor (Bootstrap)', 'openDialogBootstrap')
-    .addItem('About me', 'openAboutSidebar')
-    .addToUi();
+    .addItem('About me', 'openAboutSidebar');
+
+  menu.addToUi();
 };
 
 export const openDialog = () => {