add manual Github release mention

Author: RRosio

README.md

@@ -365,4 +365,7 @@ Install the necessary `twine` python package
 Then to upload the package to PyPI, do:
   ```bash
   twine upload dist/*
-  ```
+  ```
+
+Lastly, you can follow the instructions [here](https://docs.github.com/en/repositories/releasing-projects-on-github/managing-releases-in-a-repository)
+to make a manual release on Github via [`jupyter_nbextensions_configurator/releases`](https://github.com/jupyter-contrib/jupyter_nbextensions_configurator/releases).