add project using this blurb to README (#67)

Author: joshuadavidthomas

README.md

@@ -22,6 +22,12 @@ Built on [gidgethub](https://github.com/gidgethub/gidgethub) and [httpx](https:/
 
 Fully supports both sync (WSGI) and async (ASGI) Django applications.
 
+## Projects using django-github-app
+
+- [psf/clabot](https://github.com/psf/clabot)
+
+Are you using django-github-app in a production application? Open a PR to add it to this list!
+
 ## Requirements
 
 <!-- [[[cog