Add indicator of unread messages while in call
Add indicator of unread messages while in call

When in a call and the sidebar is collapsed, whenever new unread
messages arrive, a bubble will be displayed on top of the button that
opens the sidebar.

If a mention exists, the bubble will appear highlighted.

Whenever a new unread message or new mention arrives while in a call
with the sidebar closed, a notification will appear once.

Signed-off-by: Vincent Petry <87e1f221a672a14a323e57bb65eaea19d3ed3804@nextcloud.com>
Co-authored-by: Joas Schilling <2bd0f8145e76cd3bbdf3e5ce202d948f0d8b62eb@users.noreply.github.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed