Add markdown template for release umbrella issues (#5055)

Co-authored-by: Anbraten <6918444+anbraten@users.noreply.github.com>

.github/release_template.md

@@ -0,0 +1,33 @@
+<!-- markdownlint-disable MD041 -->
+
+### Prerequisites
+
+- [ ] MAJOR: Check `docs/src/pages/migrations.md`
+  - [ ] Check whether it contains all the necessary migration steps and recommended actions for users and administrators
+  - [ ] Check whether the steps refer to the associated pull requests or issues
+  - [ ] Ensure that the steps are clear and describe the actions required for the migration
+    - Good: "Rename your `branch` configuration option to `when.branch` (PR#123)"
+    - Bad: "Remove the `branch` configuration option in favor of `when.branch`"
+    - If possible, provide background information so users can understand the change
+- [ ] MAJOR: Create a blog entry in `docs/blog/` that highlights the most important changes and includes a link to the release notes.
+- [ ] Prepare docs PR for new version and delete old versions (keep only the last three minor versions for the current major version)
+  - [ ] Copy `docs/docs` to `docs/versioned_docs/version-<version>` and delete old versions
+  - [ ] Create `docs/versioned_sidebars/version-<version>-sidebars.json` and delete old ones
+  - [ ] Add new version to `docs/versions.json` and delete old versions
+  - [ ] Add new version to the version list in `docs/src/pages/versions.md`
+- [ ] Announce the release in the maintainer chat and ask for pending blockers
+
+### Release
+
+- [ ] Test the latest container images to make sure they work as expected
+- [ ] Update `https://ci.woodpecker.org` to the latest version of `next` and verify that it works as expected
+- [ ] Merge the release PR to start the release pipeline
+
+### Post-release
+
+- [ ] Merge the docs PR
+- [ ] Release the Helm Chart. If renovate has not created the upgrade PR already, manually trigger it from the Dependency Dashboard.
+- [ ] Announce release in relevant chats and on social media platforms
+  - [ ] Mastodon (check if already posted from the release pipeline)
+  - [ ] Matrix
+  - [ ] Twitter

.markdownlint.yaml

@@ -56,8 +56,6 @@ MD013:
   tables: false
   # Include headings
   headings: true
-  # Include headings
-  headers: true
   # Strict length checking
   strict: false
   # Stern length checking
@@ -73,7 +71,7 @@ MD022:
 # MD024/no-duplicate-heading/no-duplicate-header - Multiple headings with the same content
 MD024:
   # Only check sibling headings
-  allow_different_nesting: true
+  siblings_only: true
 
 # MD025/single-title/single-h1 - Multiple top-level headings in the same document
 MD025: