Use markdown mermaid diagrams in documentation

[nuclearcat]

Mermaid diagrams supported in github markdown parsing, and probably hugo can support it too, so we can have nice diagrams like this:

This link clickable and points to live editor:

[JenySadadia]

Yes, we already have a bunch of mermaid digrams for API and Pipeline docs. See https://kernelci.org/docs/api/pipeline-details/