Add a license

[TheFrenchGhosty]

The website currently doesn't have a license, we ideally need one.

Two option:

CC BY-ND 4.0: Derivative aren't allowed ( https://jellyfin.org/ is an example of a website using it)

CC BY-NC-SA 4.0: Derivative mustn't be used for commercial purpose ( https://libera.chat/ - or even https://pussthecat.org - are examples of a websites using it)

I'm leaning a bit more toward BY-ND, but both are fine in my opinion.