Screenshares follow-up

[marcoambrosini]

• LocalVideo should show the screen in a similar way to how it is done in Video, so the local screen share is visible in grid view too
• When a participant has both video and a screen share is followed the stripe shows only the placeholder; in that case maybe it would be better to show the video and also a placeholder showing that it is the participant being followed
• There is no name identifying whose screen is being viewed, and there is no button to stop following a participant if the participant is sharing the screen. The same text and button used for videos might not be a good option, though, as in a screen share you may want to be able to fully see the screen (for example, to read something in the screen of the other participant).
• Also, when a screen share is no longer followed the screen share will be shown anyway (or a different one, but always a screen share) no matter who is speaking. Therefore if there is no button to stop following the screen share it may not be a big problem.