Support react-refresh and shared client/server types (#98)

- Adds support for react-refresh through `@pmmwh/react-refresh-webpack-plugin`. Updated webpack config to support this. Means entire app is no longer refreshed on changes, only individual components, and state is maintained.
- React refresh removes need for `google-apps-script-webpack-dev-server` package
- In client code, support for server function autocomplete through use of gas-client 1.0.0. Requires certain files to be typescript .ts files
- Remove need for "global" exports in main server file through updated gas-webpack-plugin

dev/index.js

@@ -1,8 +1,6 @@
 import React, { useEffect } from 'react';
 import ReactDOM from 'react-dom';
-import server from '../src/client/utils/server';
-
-const { serverFunctions } = server;
+import { serverFunctions } from '../src/client/utils/serverFunctions.ts';
 
 const { FILENAME, PORT } = process.env;
 
@@ -54,10 +52,7 @@ const DevServer = () => {
           position: 'absolute',
         }}
         ref={iframe}
-        // The "/gas/" path here must match the path where the custom dev server is being loaded.
-        // See webpack.config.js "devServer" "before" settings.
-        // Filename extension "-impl" must match webpack.config.js clientConfigs filename settings for development.
-        src={`https://localhost:${PORT}/gas/${FILENAME}-impl.html`}
+        src={`https://localhost:${PORT}/${FILENAME}-impl.html`}
       />
     </div>
   );