Add usage example to readme

Author: webbertakken

README.md

@@ -22,8 +22,17 @@ implementations.
 
 ## Usage
 
-TBD
+When your workflow is finished, or ends in a failure; return the license.
 
+Add this job to your workflow:
+
+```yaml
+ # Return License
+ - name: Return license
+ uses: webbertakken/unity-return-license@v0.1
+ env:
+ UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
+```
 
 ## More actions