Merge pull request #714 from reviewdog/update-release-doc

doc: add Hot Fix Release process

.github/CONTRIBUTING.md

@@ -12,3 +12,21 @@ You can create a Pull Request to release a new version.
    new version depending on the label and create a new release on merging the
    Pull Request.
 5. Check the release workflow and verify the release. [![release](https://github.com/reviewdog/reviewdog/workflows/release/badge.svg)](https://github.com/reviewdog/reviewdog/actions?query=workflow%3Arelease)
+
+### Hot Fix Release
+
+If you find a severe issue and want to release a fix ASAP without unreleased features,
+you may want to follow the hot-fix release process instead of the usual release flow.
+
+It's mostly similar to the usual release flow, but you need to change the target branch of release pull request.
+
+1. Create a fix and merge it into master.
+2. Create a release branch (`release-v{major}.{minor}`) based on the latest semver release `v{major}.{minor}.{patch}` if there is no exisisting release branch.
+  - You need write permission to reviewdog repository to push the release branch.
+3. Create **another release request branch** (any name is fine) and update [CHANGELOG.md](../CHANGELOG.md).
+4. Create a pull request from the release request branch to **the release branch** (`release-v{major}.{minor}`) instead of master.
+5. Attach `bump:patch` label.
+6. [The release workflow](./workflows/release.yml) automatically tag a
+   new hot-fix version and create a new release on merging the Pull Request.
+7. Check the release workflow and verify the release. [![release](https://github.com/reviewdog/reviewdog/workflows/release/badge.svg)](https://github.com/reviewdog/reviewdog/actions?query=workflow%3Arelease)
+8. Merge the release branch into master to include the CHANGELOG.md update.