Add md documentation to be consumed by Toolkit docs app

[MrDinsdale]

Following the recent changes to Toolkit docs (see toolkit docs examples) it would be good to also add documentation on Supercell to be consumed by the Toolkit app.

Would these docs belong here or within Toolkit? It makes sense for the md docs to live within the relevant repo so changes to docs can be made in tandem with changes to functionality. It could be a little confusing to anyone viewing this repo in isolation though so would probably require a section to be added to the README.md.

Thoughts?

[joe-bell]

It makes sense for the md docs to live within the relevant repo so changes to docs can be made in tandem with changes to functionality.

Absolutely 👌