[Announcement] Azurite branching strategy change

Previously, Azurite V3 repo has 2 branches. Master branch is release branch which is always align with latest published released package. Dev branch accepts daily development commits. We are considering dropping dev branch and only keep master branch as develpment branch:

* Latest master branch commit is same/ahead of latest public released commit
* Every release will tag release commit
* All PRs should send to master
* Only rebase & squash merge into master

Please comments if any concerns.

TODO:

- [x] update contribution.md accordingly