Mark all rooms as read

[BurnyBoi]

Is your feature request related to a problem? Please describe.
Too many unread rooms to manually clear the unread marker on each.

Describe the solution you'd like
Add a way to mark all rooms as read to the UI

Describe alternatives you've considered
Mark all option exists in Element Web (If the list of unread rooms is above a certain amount) so you can do it there then come back to SchilidiNext.

Additional context
Element X feature request: element-hq/element-meta#2682