"Mark as read" action for Talk notifications

Is your feature request related to a problem? Please describe.
When you are in a bunch of Talk rooms, you get a lot of notifications – especially when coming back from vacation. Currently it is nice to be able to go through the notifications popover in the header to check them, and also x them away.

The issue is that when you do x them, the conversation in Talk is still unread (blue bubble). Then you need to go through Talk and manually click those conversations to mark them as read that way.

Describe the solution you'd like
A "mark as read" action for Talk notifications which many other messengers (especially mobile) have, which marks the mention as read. This would then mark the @-mention in the conversation as read, leading to a grey bubble instead of a blue one. (Alternatively, the whole conversation could be marked as read, especially if there are no other notifications pertaining to that conversation.)

Describe alternatives you've considered
Marking as read on clicking the "x", but that is not expected, since the "x" is for dismissing the notification only.

@marcoambrosini @nickvergessen what do you think? This is something I notice every time coming back from vacation when there are a lot of notifications.