[docs]: Add Tokens pages

[bennypowers]

Implement docs pages for tokens, using the new 11ty plugin

https://xd.adobe.com/view/54aea3e4-4896-4823-9833-e40f1195e7c6-01fd/grid

One approach to implementing search:
https://claytonerrington.com/blog/adding-a-basic-search/
or maybe https://pagefind.app/

[bennypowers]

@coreyvickery. The XD for this is still locked, I have to type the text content in manually.

Best would be for you to just commit directly to #717

you can press the . key when looking at that pr, or change the url from github.com to github.dev, then just edit the markdown file (docs/tokens/index.md)

The listing cards on /tokens can't be edited from here, we need to add that information to the tokens repo. I suggest that we add two new props to the docs metadata in tokens, for each category: summary and thumbnail: these would correspond to the body content and header image in listing cards, a la /elements, /patterns