docs: updated release notes for 5.1

docs/release-notes/release-notes-5.1.0.rst

@@ -16,13 +16,16 @@ New Features
 - Email based log-in. RhodeCode now allows to log-in using email as well as username for main authentication type.
 - Ability to replace a file using web UI. Now one can replace an existing file from the web-ui.
 - GIT LFS Sync automation. Remote push/pull commands now can also sync GIT LFS objects.
+- Added ability to remove or close branches from the web ui
+- Added support for S3 based archive_cache based that allows storing cached archives in S3 compatible object store.
+
 
 General
 ^^^^^^^
 
 - Upgraded all dependency libraries to their latest available versions
 - Repository storage is no longer controlled via DB settings, but .ini file. This allows easier automated deployments.
-
+- Bumped mercurial to 6.7.4
 
 Security
 ^^^^^^^^
@@ -34,6 +37,7 @@ Performance
 
 - Introduced a full rewrite of ssh backend for performance. The result is 2-5x speed improvement for operation with ssh.
   enable new ssh wrapper by setting: `ssh.wrapper_cmd = /home/rhodecode/venv/bin/rc-ssh-wrapper-v2`
+- Introduced a new hooks subsystem that is more scalable and faster, enable it by settings: `vcs.hooks.protocol = celery`
 
 
 Fixes