Fully customizable media player controls using web components

[wilaw]

dash.js has a single UI component, provided by Akamai many years ago. While suffucient for many, it would be good to have an alternate choice for player UI. This project https://github.com/muxinc/media-chrome by Steve Heffernan looks very interesting in this regard. It provides fully customizable media player controls using web components (native custom elements). License is MIT. Might it be something dash.js could leverage?

[heff]

Thanks Will, excited to see interest on this front. Happy to help where I can. @cjpillsbury is just finishing up a pretty solid accessibility pass.

[dsilhavy]

Related to #4234