Broken TODO docs link in README

[justinTM]

https://github.com/grafana/scuemata/blob/main/TODO

[sdboyer]

Yup! That's a genuine TODO, as i try to bootstrap a docs site amidst a pile of other things with this work. But hey, here's some incremental docs, which should continue expanding over the coming days :) https://github.com/grafana/scuemata/blob/main/docs/authoring/authoring.md

[sdboyer]

Closing this as it's a known TODO

Pile of issues and more docs coming soon