Add basic glossary handling

[Diolor]

Closes OWASP/mastg#3390

Summary

It can be tested together with TG branch: https://github.com/Diolor/mastg/tree/add-glossary

I’ve explored two possible approaches for adding the glossary:
1. One Markdown file per term
• Each term has its own dedicated page.
• Makes terms individually linkable and easier to maintain or expand with additional content (e.g., references, examples).
2. A single Markdown file with all terms
• All terms are collected in one place.
• Benefits include having a built-in table of contents and a single page for quick browsing.

After weighing the trade-offs, I’ve selected the first option (one Markdown file per term) to provide modularity, maintainability, and better deep-linking support.

The position of the Glossary has been decided to appear at the top level of the navigation structure, making it directly accessible without nesting under other sections.

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Glossary list view

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Single item view

We can optionally support cwe and NIST deeplinks via markdown headers:

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References from other locations

We can deeplink terms with @MAVTG-TERM-xxxx.md:

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Final thoughts

This section is intended as a glossary, not an index. However, cross-references can still be valuable. For each glossary entry, we can include pointers to where the term is used throughout the content. Feedback and suggestions on this approach are welcome.