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

README.md

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   <a href="" rel="noopener">
  <img width="400" src="https://i.imgur.com/83Y7bWN.png" alt="React & Google Apps Script logos"></a>
 </p>
+<p align="center"><i>
+  Update 2022: Now with support for React v17 and React Fast Refresh
+</i></p>
 
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 </div>
 
-<p align="center"> This is your boilerplate project for developing React apps inside Google Sheets, Docs, Forms and Slides projects. It's perfect for personal projects and for publishing complex add-ons in the G Suite Marketplace.
+<p align="center"> 🚀 This is your boilerplate project for developing React apps inside Google Sheets, Docs, Forms and Slides projects. It's perfect for personal projects and for publishing complex add-ons in the G Suite Marketplace.
 </p>
 
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@@ -189,6 +192,8 @@ After running the start command, navigate to your spreadsheet and open one of th
 
 <img width="100%" src="https://i.imgur.com/EsnOEHP.gif">
 
+Support for [Fast Refresh](https://github.com/pmmmwh/react-refresh-webpack-plugin) now means that only modified components are refreshed when files are changed, and state is not lost.
+
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 ### 🔍 Using React DevTools <a name="dev-tools"></a>