Add a Pop Out button to Video Rooms Beta

### Your use case

#### What would you like to do?
pop out the element-call window into a new tab.

#### Why would you like to do it?

jitsi had a popout button. me and my friends would use it a lot. other people would also prefer using the video rooms in-client as opposed to popping out having the feature this way lets people of either preference join the same call room and still communicate.

#### How would you like to achieve it?

possibly the same way as the jitsi widgets did. having a little button in the top right, out of the way.
or it could be placed in the More... menu of the element-call widget. it doesn't exactly really matter where, as long as the button is easy and accessible and out of the way.

### Have you considered any alternatives?

i wouldnt really call it an alternative, but the next best thing i could find was opening
[call.element.io](https://call.element.io/room/#roomid:call.ems.host) and just having it as a floating window in the corner of the client. this is very unoptimal as i havent found a way to "pop out" the player, or set a video rooms call ID to any given #roomid, which that would probably work too, as then at least you can get the url.

### Additional context

i just think its an important feature to have, more than a few people i know use it on jitsi and other things on a regular basis.