Mention clj-debugger in the README

Author: bbatsov

README.md

@@ -165,6 +165,7 @@ Let's also acknowledge some of the projects leveraged by cider-nrepl:
 * [tools.trace](https://github.com/clojure/tools.trace) - for tracing
 * [tools.namespace](https://github.com/clojure/tools.namespace) - for namespace reloading
 * [cljfmt](https://github.com/weavejester/cljfmt) - for code formatting
+* [clj-debugger](https://github.com/razum2um/clj-debugger) - for debugging
 
 ## License