🎨 Update .gitignore

Problem:
- Cache directories made by various tools can be made in any directory, but are
  only ignored in the root directory.
- Conventional directory names containing "build" or "venv" should be ignored.

Solution:
- Alter .gitignore to properly ignore cache directories and conventionally-named
  venv/build directories.

Author: elbeno

.gitignore

@@ -1,19 +1,26 @@
-build/
-/cmake-build-*
-/venv
-/.vscode
-/.idea
-/.cache
-/.DS_Store
-.clang-format
-.clang-tidy
-.cmake-format.yaml
-CMakePresets.json
+# ignore all directories that start with .
+**/.*/
+
+# ignore conventionally-named build directories
+**/build*/
+**/*build/
+# and some other build directories
+**/cmake-build-*/
+
+# ignore conventionally-named python virtual env directories
+# (this is only necessary before Python 3.13)
+**/venv*/
+**/*venv/
+# and __pycache__ directories
+**/__pycache__/
+
+# ignore files provided by CICD
+/.clang-format
+/.clang-tidy
+/.cmake-format.yaml
+/CMakePresets.json
 /toolchains
-__pycache__
-.mypy_cache
-.pytest_cache
-.hypothesis
-requirements.txt
-docs/puppeteer_config.json
-docs/mermaid.conf
+/mull.yml
+/requirements.txt
+/docs/puppeteer_config.json
+/docs/mermaid.conf