docs(mermaid): document the controls, fullscreen and align arguments

[markdumay]

Summary

The mermaid component page stated "The shortcode does not support any arguments" — stale, since it now supports controls, fullscreen, and align.

Replace that with:

• the auto-generated args table ({{< args structure="mermaid" group="shortcode" >}}), which renders from mod-mermaid's data/structures/mermaid.yml — controls and align inherit their canonical mod-utils definitions, fullscreen is mermaid-specific;
• a live example showing {{< mermaid controls=true fullscreen=true >}}.

Uses the same {{< args … >}} pattern as the other component pages (e.g. button) and the same {{</* mermaid */>}} escaping as the page's existing diagram examples.

[markdumay]

🎉 This PR is included in version 1.14.0 🎉

The release is available on GitHub release

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