Update Python.gitignore

Add ruff cache. 
ruff tool: https://github.com/charliermarsh/ruff
ruff is becoming a very popular tool often run in pre-commit and aim to replace Flake8 (plus dozens of plugins), isort, pydocstyle, yesqa, eradicate, pyupgrade, and autoflake, all while executing tens or hundreds of times faster than any individual tool.

Author: csauge

Python.gitignore

@@ -158,3 +158,6 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+# Ruff stuff:
+.ruff_cache/