Add 21.05_announce

doc/source/releases/21.05_announce.rst

@@ -1,12 +1,45 @@
 
-:orphan:
-
 ===========================================================
 May 2021 Galaxy Release (v 21.05)
 ===========================================================
 
+.. include:: _header.rst
 
-Schedule
+Highlights
 ===========================================================
- * Planned Freeze Date: 2021-05-03
- * Planned Release Date: 2021-05-24
+
+**Feature1**
+  Feature description.
+
+**Feature2**
+  Feature description.
+
+**Feature3**
+  Feature description.
+
+Also check out the `21.05 user release notes <21.05_announce_user.html>`__
+
+Get Galaxy
+==========
+
+The code lives at `GitHub <https://github.com/galaxyproject/galaxy>`__ and you should have `Git <https://git-scm.com/>`__ to obtain it.
+
+To get a new Galaxy repository run:
+  .. code-block:: shell
+
+      $ git clone -b release_21.05 https://github.com/galaxyproject/galaxy.git
+
+To update an existing Galaxy repository run:
+  .. code-block:: shell
+
+      $ git fetch origin && git checkout release_21.05 && git pull --ff-only origin release_21.05
+
+See the `community hub <https://galaxyproject.org/develop/source-code/>`__ for additional details on source code locations.
+
+Release Notes
+===========================================================
+
+.. include:: 21.05.rst
+   :start-after: announce_start
+
+.. include:: _thanks.rst