Update releasing notes (#2243)

RELEASING.md

@@ -15,10 +15,13 @@ Note: These steps should be done directly in the pinterest/ktlint repository, no
 6. Push your changes to the branch, and merge it to `master`.
 7. Update your local `pinterest/ktlint` `master` branch; verify you see the `gradle.properties` and `CHANGELOG.md` changes locally.
 8. Add a tag with the new release version, and push it directly to remote (e.g. `git tag 0.50.0 && git push origin 0.50.0`). This will kick off the [Release workflow](https://github.com/pinterest/ktlint/actions/workflows/release.yml).Important: when you get an error like `HttpError: refusing to allow a Personal Access Token to create or update workflow '.github/workflows/automerge-triggers.yml' without 'workflow' scope`, the Github personal access token is most likely expired. When this happens on the bump of the Homebrew formula, the personal access token of @shashachu needs to be updated.
-9. Close and release the repo on Sonatype. (Only Pinterest employees can do this.)
+9. Close and release the repo on Sonatype. Only Pinterest employees can do this. Wait with steps below until artifacts are published on https://central.sonatype.com/search?q=ktlint&sort=published
 10. The `.announce` script has created the `<release>-update-refs` branch in the repo. Create a new pull request (https://github.com/pinterest/ktlint/compare) and merge it to master.
 11. Merge of branch `<release>-update-refs` to master starts the `Publish release documentation` and `Publish snapshot documentation` workflows. Check that both workflows succeed (https://github.com/pinterest/ktlint/actions). Also check that the documentation has actually been published on https://pinterest.github.io/ktlint/latest.
-12. Update `gradle.properties` with the new `SNAPSHOT` version, and add the section below to the top of `CHANGELOG.md` and commit. (This can be done directly in the main repo or in your fork.)
+12. Verify that documentation of new release is published correctly.
+13. Verify that the published documentation does not contain broken links with [Broken Link Checker Tool](https://www.deadlinkchecker.com/website-dead-link-checker.asp).
+14. Announce release on Ktlint Slack channel 
+15. Update `gradle.properties` with the new `SNAPSHOT` version, and add the section below to the top of `CHANGELOG.md` and commit. (This can be done directly in the main repo or in your fork.)
 ```markdown
 ## Unreleased
 
@@ -30,8 +33,3 @@ Note: These steps should be done directly in the pinterest/ktlint repository, no
 
 ### Changed
 ```
-
-## After release of documentation
-
-[The documentation for KtLint](https://pinterest.github.io/ktlint/) should be checked for dead links.
-Follow the instructions for building the documentation in `/documentation/readme.md`, and use a tool such as [Broken Link Checker Tool](https://www.deadlinkchecker.com/website-dead-link-checker.asp) to find broken links.