Let's Fix These PeerTube Accessibility Issues

*Note:* For whatever reason, my microphone cut out at some points. I think the video is still understandable though, so I'm leaving it. I really love PeerTube and the video streaming platform they're creating and I want to see it grow. So this is my contribution to the community. I'm almost completely blind and although 90% of the PeerTube UI is accessible, I thought I'd do my bit to clarify which parts are not. The GitHub issue is [#797](https://github.com/Chocobozzz/PeerTube/issues/797).