doc: adding Unity License Setup

CONTRIBUTING.md

@@ -13,6 +13,18 @@ and let our peers review the code before it gets merged.
 - We try to prefix our commit messages with a word that quickly tells the reader where the change happened. Examples are `editor`, `doc`, `<component-name>`, etc.
 - Changes that touch the core project should be unit-tested. 
 
+### Unity License Setup For Automated Testing
+
+It's preferred to make the automated tests run when creating your PR. Since Unity needs a license key (which can be obtained with a free account), you'll need to configure your fork to use the correct secrets.  You will need to use a Personal license and request a key on behalf of GitHub: 
+
+1. Run the `License` workflow by clicking the `Run workflow` button in the `Actions` tab. When the workflow completes, download and unzip the `Unity_v2021.3.0f1.alf` artifact. 
+2. Visit [license.unity3d.com](https://license.unity3d.com), sign in, and upload the `Unity_v2021.3.0f1.alf` file.
+3. You should now receive your license file (`Unity_v2021.x.ulf`) as a download. 
+4. Open `Github` > `<Your repository>` > `Settings` > `Secrets`
+- Create the following secret:
+  - `UNITY_LICENSE` - (Copy the contents of the `Unity_v2021.x.ulf` license file here)
+5. Delete the `License` workflow run by selecting `Delete workflow run` in the `...` menu.  
+
 ## Code Style 
 
 We aren't too picky about code style. Just start reading our code and you'll get the hang of it. There