chore: update CONTRIBUTING.md (#4703)

Signed-off-by: kostas <[email protected]>

Author: kostasrim

CONTRIBUTING.md

@@ -21,8 +21,9 @@ cd build-dbg && ninja dragonfly
 ```sh
 cd dragonfly   # project root
 
-# Make sure you have 'pre-commit' and 'clang-format' installed
+# Make sure you have 'pre-commit', 'clang-format' and black is installed
 pip install pre-commit clang-format
+pip install pre-commit black
 
 # IMPORTANT! Enable our pre-commit message hooks
 # This will ensure your commits match our formatting requirements