better looking example

[facundoolano]

Create a new example with a sophisticated client. Consider clojurescript/re-frame.

• [ ] unlimited group video.
• [ ] bulma for css, pick a good background.
• [ ] video containers should resize dynamically to fill the screen.
• [ ] video containers shouldn't downsize when resolution is changed.
• [ ] smaller, mirrored local stream.
• [ ] set the username (maybe with a random default).
• [ ] display the username in the video container.
• [ ] audio/video on/off buttons.
• [ ] add a screenshot to the readme.

[facundoolano]

review suggestions from https://simplewebrtc.com/notsosimple.html