Creating a better sample

[alexandercerutti]

The current sub37 sample is quite empty and not very useful. Also, it doesn't let people that don't know WEBVTT format (or any other future format) to play with the sample.

We should create something a little bit complex, also perhaps by evaluating whether to use React or any other front-end framework to make things easy.

Using a front-end framework, would let us test how Web Components fix in a different ecosystem.

A couple of principles a new sample should follow:

1. We don't want to create a subtitles editor applicator, so it should be complex enough to let people play but not complex enough to be a full tool (that might be a different project).

2. People should be allowed to add new cues, maybe with both an interactive UI and raw track manipulation