Announce that the branch has been created and can be used

For more information, refer to Creating release branches for RHBQ documentation procedure.

Communicate to the team on #team-quarkus-docs Slack channel that the branch has been created:

Exciting news, team! 🎉

The new documentation release branch, quarkus-3-15, has officially been created! 🥳

You can now sync it to your local machines with the following commands:
 
git fetch upstream quarkus-3-15
git checkout -b quarkus-3-15 upstream/quarkus-3-15