* Reworked full screen CSS layout for the chat.html, still using Bulma
components with some custom CSS Grid.
* Duplicate username handling: server can push a new username to change
the client's selection.
* Who List sync between clients.
* Local video casting works so far - plays back your camera in the local
feed. Your video broadcasting boolean is synced to backend, which
lights up the video button in the Who List.
