[x] Add "mark as read" action to show instead of "mark as unread" when the chat is already unread
[x] which also updates the read receipt (and thus also marks chats as read that had new messages)
[x] After using the "mark as (un)read" actions, the chat entry is still rendered in some kind of selected state, which makes it harder to see if it actually worked. Can we remove that selected state automatically?
WIP: https://github.com/SchildiChat/matrix-react-sdk/commits/mark-as-unread
Mandatory
Nice to have