[FEATURE] Explore diagrams-as-code

[edhamiltonHO]

What is the feature or enhancement you are suggesting? We could consider supporting something like mermaid.js to make this straightforward to define in markdown

What would be the benefit of doing this? Users may want to add content to the site that includes diagrams.

Additional information Would prefer not to use javascript on the page so would be good if this could be built into the static site at build time

Please confirm the below

• [x] I have checked through the issues on the repository and this has not already been suggested

[keithkennedyHO]

Mermaid diagram branch

[keithkennedyHO]

Potentially useful plugin to consider if we choose to use Mermaid. https://github.com/KevinGimbel/eleventy-plugin-mermaid/