Add announcement steps to release-howto (#18896)

* add announcements steps to release-howto

* Also add homebrew update

Author: noerw

CONTRIBUTING.md

@@ -423,6 +423,11 @@ be reviewed by two maintainers and must pass the automatic tests.
 * And then push the tag as `git push origin v$vmaj.$vmin.$`. Drone CI will automatically create a release and upload all the compiled binary. (But currently it doesn't add the release notes automatically. Maybe we should fix that.)
 * If needed send a frontport PR for the changelog to branch `main` and update the version in `docs/config.yaml` to refer to the new version.
 * Send PR to [blog repository](https://gitea.com/gitea/blog) announcing the release.
+* Verify all release assets were correctly published through CI on dl.gitea.io and GitHub releases. Once ACKed:
+  * send a PR to the [homebrew repo](https://gitea.com/gitea/homebrew-gitea) analog to [this PR](https://gitea.com/gitea/homebrew-gitea/commit/1f9a3fe5eb75b64a96a5336665531abcbd0eef0c)
+  * bump the version of https://dl.gitea.io/gitea/version.json
+  * merge the blog post PR
+  * announce the release in discord `#announcements`
 
 ## Copyright