Documentation overhaul

[darrendignam]

Summary

This PR updates the JHOVE documentation site with a broad usability and presentation overhaul. The goal is to make the docs easier to navigate, easier to read, and more consistent across sections while keeping the existing content structure intact.

A live demo of this docs site can be seen here:
https://jhove.darrendignam.com/

What changed

• Added breadcrumbs across the docs so users can see where they are in the site hierarchy.
• Added a full documentation sidebar with hierarchical navigation for the site structure.
• Standardized front matter across docs pages so navigation metadata is consistent.
• Fixed parent/title mismatches so section pages and child pages resolve correctly in navigation.
• Added a new documentation page explaining how to edit and contribute to the docs.
• Improved the overall visual design of the docs:
  • more deliberate color usage
  • clearer navigation states
  • added dark mode

Note

• This is primarily a documentation and UX pass; no functional JHOVE application behavior is intended to change.