Add maintenance mode notice

Author: Siddhartha Bagaria

README.md

@@ -1,6 +1,17 @@
 Compilation database with Bazel [![Tests](https://github.com/grailbio/bazel-compilation-database/actions/workflows/tests.yml/badge.svg)](https://github.com/grailbio/bazel-compilation-database/actions/workflows/tests.yml) [![Migration](https://github.com/grailbio/bazel-compilation-database/actions/workflows/migration.yml/badge.svg)](https://github.com/grailbio/bazel-compilation-database/actions/workflows/migration.yml)
 ===============================
 
+
+====
+
+NOTE: This repository is now in maintenance mode. If you have a well-maintained
+fork of this repository, or an alternative implementation, please let me know
+and I will be very happy to redirect people to your repository. If you would
+like to continue contributing to this repository, please let me know and I can
+give you write access.
+
+====
+
 If you use [Bazel][bazel] and want to use libclang based editors and tools, you
 can now generate [JSON compilation database][compdb] easily without using build
 intercept hooks.  The advantage is that you can generate the database even if