Add a toggle to remove video player

[JoeWhitwellBBC]

Context
From Sutherland Labs
"Where possible, they asked for the ability to make even more use of the space available, for example by removing the black space at the top that isn’t required for audio editing"

Task

• Removing the video at the top of the interface would give the user more space on small screens.

• Set default to non video, unless video content is loaded