doc: start documentation

[pamapa]

First part of the documentation. Its a good string point, i will add additional stuff like linking, more text and other stuuff in later MRs. When we are working on specific features, we might also improve the documentation for those.

I have tested the markdown files using Visual Code.

I have more or less adapted the code from the predecessor library. I have not taken parts like: RTF, Private Fonts, which are not present here or no longer make sense. For the "private fonts" i will extend the fontresolver sample later with information to make a custom resolver and why that might be needed...

When this is merged, I will simplify the projects main README.md.