Update README.md (#847)

README.md

@@ -1,3 +1,8 @@
+# This project is now archived
+
+This project is no longer under active maintenance. It is read-only, but you can still clone or fork the repo. [Check here for further info](https://docs.github.com/en/repositories/archiving-a-github-repository/archiving-repositories).
+Please contact innereye_info@service.microsoft.com if you run into trouble with the "Archived" state of the repo.
+
 # InnerEye-DeepLearning
 
 [![Build Status](https://innereye.visualstudio.com/InnerEye/_apis/build/status/InnerEye-DeepLearning/InnerEye-DeepLearning-PR?branchName=main)](https://innereye.visualstudio.com/InnerEye/_build?definitionId=112&branchName=main)