Convert CONTRIBUTING.rst -> CONTRIBUTING.md

Author: hugovk

CONTRIBUTING.md

@@ -0,0 +1,26 @@
+# How to release
+
+- Update `CHANGELOG.md`
+- Bump version (YYYY.MM) in `python_docs_theme/__init__.py`
+- Commit
+- Push to check tests pass on
+  [GitHub Actions](https://github.com/python/python-docs-theme/actions)
+- Go to https://github.com/python/python-docs-theme/releases
+- Click "Draft a new release"
+- Click "Choose a tag"
+- Type the next YYYY.MM version (no leading zero) and
+  select "**Create new tag: YYYY.MM** on publish"
+- Leave the "Release title" blank (it will be autofilled)
+- Click "Generate release notes" and amend as required
+- Click "Publish release"
+- Check the tagged [GitHub Actions build](https://github.com/python/python-docs-theme/actions/workflows/pypi-package.yml)
+  has deployed to [PyPI](https://pypi.org/project/python-docs-theme/#history)
+
+# Makefile usage
+
+This project includes a simple Makefile for syncing changes to the theme with
+the main CPython repository. Run `make help` for details on available rules.
+
+There is one configurable variable, `CPYTHON_PATH`, which should be the path
+to the CPython repository on your machine. By default, it points to
+`../cpython`.