Add a video to the README showing how Dionysus looks and works

[frblo]

It's always nice when checking out an application on GitHub to see how it's intended to work without having to actually download and run the application. We should add a video (gif or mp4) which shows this.

[Frequinzy]

Since the UI is still changing do we want to add this to the README that will require to be kept in sync?

[frblo]

I mean it should be added to the README, and probably be updated in case of major UI changes, yes.