fix: updated contributing docs (#301)

CONTRIBUTING.md

@@ -50,7 +50,10 @@ cd titanoboa
 ```bash
 python -m venv venv
 source venv/bin/activate
+# Install dev requirements
 pip install -r dev-requirements.txt
+# Install prod requirements (in the pyproject.tom)
+pip install . 
 ```
 
 *Note: When you delete your terminal/shell, you will need to reactivate this virtual environment again each time. To exit this python virtual environment, type `deactivate`*