fix: gitignore live config, add example template

Untrack config/derp.toml to avoid leaking credentials.
Ship config/derp.toml.example as the reference template.

.gitignore

@@ -0,0 +1,13 @@
+__pycache__/
+*.pyc
+*.pyo
+*.egg-info/
+dist/
+build/
+.venv/
+.eggs/
+*.egg
+.ruff_cache/
+.pytest_cache/
+.mypy_cache/
+config/derp.toml