Change from MkDocs to Zensical

[SamDuffield]

Closes #221

It works with mkdocs.yaml but we may want to move to zensical.toml for clarity.

[Sahel13]

Not sure if this is a local issue for me, but when I first serve the site with zensical, it shows a generic home page, and not what we have in index.md. Also the links to the API references for cuthbert and cuthbertlib are broken, not sure why.

Edit: The issue with the homepage appears to be because we have a readme inside the docs, and zensical doesn't support excluding a page yet.

[theorashid]

I think we might as well move to zensical.toml if we're going forward with this.

There should be a README.md in the docs folder and it contains mkdocs commands anyway. The CONTRIBUTING.md covers zensical serve so we can safely remove it.

[SamDuffield]

I removed docs/README.md and moved it's content into CONTRIBUTING.md so that issue should be fixed.

The cuthbert API and cuthbertlib API links however is quite strange, I've had a play around and can't figure out why that's not working grr

[Sahel13]

Changing the folder name from cuthbert_api to api_cuthbert solved the issue XD I don't know if this is a bug with zensical

[SamDuffield]

Changing the folder name from cuthbert_api to api_cuthbert solved the issue XD I don't know if this is a bug with zensical

oh no way that's hilarious! I had removed the underscore in case that was the problem somehow but not thought of this lol

you wanna push the fix? (feel free)