Use Reuse for specifying licenses of content

[kakaroto]

Need to look into this, but looks pretty nice : https://reuse.software/
Allows setting multiple licenses per files and stuff, which can then generate (I think) an overview of which licenses and contributors are used by a project.

This would be to basically replace/auto-generate this : https://github.com/kakaroto/Beyond20#license

Example repo where it's used : https://git.f3l.de/dungeonslayers/ds4