[Chore] Documentation

[noraj]

Describe the solution you'd like

Actually except the README there is no documentation of the project. I suggest to use a staticgen documentation tool. For example Docsify.js allows to create documentation in markdown that is directly rendered client-side in the browser so unlike classical staticgen you don't even need to have a CI that bild the documentation website, you can directly host docsify unders docs/ and let GitHub pages serve it. Having documentation website will allow to explain more in depth some install steps, add more screenshot, add a usage guide, etc. I'll glady contribute to the doc once a website will be in place.