docs/attestation: use mermaid to render communications

[osresearch]

Enable the mermaid plugin so that communication diagrams can be included in the markdown documentation.

[osresearch]

mermaid isn't perfect, although it seems to do a decent job of turning the text into diagrams. One nice feature is that they are not images -- the diagrams are SVG so they will still show up in google searches or find-in-page functions.

[nicowilliams]

Nice!

[nicowilliams]

Does GH support this? Looking at docs/attestation.md in this branch, it looks like it does not.

[osresearch]

unfortunately gh pages does not support it, so they don't render in the previews. if you have a local checkout you can render them with:

pip3 install -r requirements.txt
mkdocs serve --dirtyreload

You can also drop the text into https://mermaid-js.github.io/mermaid-live-editor/edit/ to see a rendering of the diagram. Example with a full diagram in the URL

[osresearch]

I've gone ahead and merged this so that it will be visible and we can discuss where else we need diagrams.