Add release checklist

RELEASING.md

@@ -0,0 +1,29 @@
+# Release Checklist
+
+- [ ] check tests pass on [GitHub Actions](https://github.com/python/cherry-picker/actions)
+      [![GitHub Actions status](https://github.com/python/cherry-picker/actions/workflows/main.yml/badge.svg)](https://github.com/python/cherry-picker/actions/workflows/main.yml)
+
+- [ ] Update [changelog](https://github.com/python/cherry-picker#changelog)
+
+- [ ] Go to [Releases page](https://github.com/python/cherry-picker/releases) and
+
+  - [ ] Click "Draft a new release"
+
+  - [ ] Click "Choose a tag"
+
+  - [ ] Type the next `cherry-picker-vX.Y.Z` version and select "**Create new tag: cherry-picker-vX.Y.Z** 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/cherry-picker/actions/workflows/deploy.yml)
+      has deployed to [PyPI] (https://pypi.org/project/cherry_picker/#history)
+
+- [ ] Check installation:
+
+```bash
+python -m pip uninstall -y cherry_picker && python -m pip install -U cherry_picker && cherry_picker --version
+```