Add Pythonic things to .git_ignore

- from https://github.com/github/gitignore/blob/master/Python.gitignore

.git_ignore

 entity_update.tsv
+
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/