Add Backstage (#3305)

Co-authored-by: Sindre Sorhus <[email protected]>

Author: shano

readme.md

@@ -168,6 +168,7 @@
 - [Uno Platform](https://github.com/MartinZikmund/awesome-uno-platform#readme) - Open-source .NET UI platform for building cross-platform apps.
 - [Google Cloud](https://github.com/GoogleCloudPlatform/awesome-google-cloud#readme) - Cloud computing services by Google.
 - [Firebase Genkit](https://github.com/xavidop/awesome-firebase-genkit#readme) - An open-source framework for building AI-powered apps and features.
+- [Backstage](https://github.com/shano/awesome-backstage#readme) - Open-source platform for building Internal Developer Portals that unify tools and workflows.
 
 ## Programming Languages