core: Add ruff rules D (docstring) (#29406)

This ensures that the code is properly documented:
https://docs.astral.sh/ruff/rules/#pydocstyle-d

Related to #21983

libs/core/scripts/check_imports.py

@@ -1,3 +1,5 @@
+"""Script to check if python modules can be imported."""
+
 import random
 import string
 import sys