Add CHANGELOG entry for REPL tab completion

Author: jpwoodbu

CHANGELOG.md

@@ -104,6 +104,7 @@ END_UNRELEASED_TEMPLATE
 
 {#v0-0-0-added}
 ### Added
+* (repl) Default stub now has tab completion. ([#3114](https://github.com/bazel-contrib/rules_python/pull/3114)). 
 * (pypi) To configure the environment for `requirements.txt` evaluation, use the newly added
   developer preview of the `pip.default` tag class. Only `rules_python` and root modules can use
   this feature. You can also configure custom `config_settings` using `pip.default`.