Add template for quarterly release issue

Author: aclark4life

.github/ISSUE_TEMPLATE/RELEASE.md

@@ -0,0 +1,45 @@
+---
+name: Release
+about: Schedule a release
+---
+
+## Main Release
+
+Released quarterly on January 2nd, April 1st, July 1st and October 15th.
+
+* [ ] Open a release ticket e.g. https://github.com/python-pillow/Pillow/issues/3154
+* [ ] Develop and prepare release in `main` branch.
+  * [ ] Add release notes for 11.2.1 https://github.com/python-pillow/Pillow/pull/8885
+* [ ] Check [GitHub Actions](https://github.com/python-pillow/Pillow/actions) to confirm passing tests in `main` branch.
+* [ ] Check that all the wheel builds pass the tests in the [GitHub Actions "Wheels" workflow](https://github.com/python-pillow/Pillow/actions/workflows/wheels.yml) jobs by manually triggering them.
+* [ ] In compliance with [PEP 440](https://peps.python.org/pep-0440/), update version identifier in `src/PIL/_version.py`
+* [ ] Run pre-release check via `make release-test` in a freshly cloned repo.
+* [ ] Create branch and tag for release e.g.:
+  ```bash
+  git branch [[MAJOR.MINOR.PATCH]]
+  git tag [[MAJOR.MINOR.PATCH]]
+  git push --tags
+  ```
+* [ ] Check the [GitHub Actions "Wheels" workflow](https://github.com/python-pillow/Pillow/actions/workflows/wheels.yml) has passed, including the "Upload release to PyPI" job. This will have been triggered by the new tag.
+* [ ] Publish the [release on GitHub](https://github.com/python-pillow/Pillow/releases).
+* [ ] In compliance with [PEP 440](https://peps.python.org/pep-0440/), increment and append `.dev0` to version identifier in `src/PIL/_version.py` and then:
+  ```bash
+  git push --all
+   ```
+
+## Publicize Release
+
+* [ ] Announce release availability via [Mastodon](https://fosstodon.org/@pillow) e.g. https://fosstodon.org/@pillow/110639450470725321
+
+## Documentation
+
+* [ ] Make sure the [default version for Read the Docs](https://pillow.readthedocs.io/en/stable/) is up-to-date with the release changes
+
+## Docker Images
+
+* [ ] Update Pillow in the Docker Images repository
+  ```bash
+  git clone https://github.com/python-pillow/docker-images
+  cd docker-images
+  ./update-pillow-tag.sh [[release tag]]
+  ```