Reimplement Audio Description Overlay

[sujitv19196]

Problem

• There is an audio description overlay (src/screens/Watch/Components/Overlays/AudioDescription/index.js) but it is not used

Solution

• figure out what this is supposed to do
• implement this into the player if it seems like a good idea

[angrave]

The overlays have stuff set up for being front of video area. However would it make more sense to use the transcript area and augment the current caption with additional controls (prev sentence || repeat sentence || next sentence || play all || cancel/pause || continue/close)