Plugin dev ux improvements (#992)

Co-authored-by: kennethloeffler <kenloef@gmail.com>

CONTRIBUTING.md

@@ -16,6 +16,23 @@ You'll want these tools to work on Rojo:
 * Latest stable Rust compiler
 * Latest stable [Rojo](https://github.com/rojo-rbx/rojo)
 * [Foreman](https://github.com/Roblox/foreman)
+* [Luau Language Server](https://github.com/JohnnyMorganz/luau-lsp) (Only needed if working on the Studio plugin.)
+
+When working on the Studio plugin, we recommend using this command to automatically rebuild the plugin when you save a change:
+
+*(Make sure you've enabled the Studio setting to reload plugins on file change!)*
+
+```bash
+bash scripts/watch-build-plugin.sh
+```
+
+You can also run the plugin's unit tests with the following:
+
+*(Make sure you have `run-in-roblox` installed first!)*
+
+```bash
+bash scripts/unit-test-plugin.sh
+```
 
 ## Documentation
 Documentation impacts way more people than the individual lines of code we write.