• resolves Add documentation for CVSS v4 DecisionTables CERTCC/SSVC#880

This PR extends

• DecisionTable to Mermaid diagrams CERTCC/SSVC#884

and adds documentation pages for the six CVSS v4 EQ set DecisionTable objects added in

• Add DecisionTable objects for CVSS v4 Equivalence Sets CERTCC/SSVC#863
• Add CVSS v4 MacroVector to Quality Severity Rating DecisionTable CERTCC/SSVC#871

Copilot Summary

This pull request adds comprehensive documentation and navigation support for modeling CVSS v4 assessment using SSVC decision tables. It introduces new pages for each CVSS v4 equivalence set, a summary page explaining the approach, and a page for the qualitative severity rating, as well as updates navigation and minor terminology corrections.

Documentation additions:

• Added detailed documentation pages for each CVSS v4 equivalence set (eq1.md through eq6.md), providing analyst decision models, visualizations, and value tables for each set. [1] [2] [3] [4] [5] [6]
• Added an overview page (index.md) explaining how CVSS v4 can be assessed using SSVC, how the equivalence sets are modeled, and how qualitative severity ratings are derived.
• Added a documentation page for the CVSS v4 Qualitative Severity Rating, including the decision model and mapping from equivalence sets to qualitative ratings.

Navigation updates:

• Updated mkdocs.yml to add a new "CVSS v4 Analyst Models" section in the navigation, linking to the new documentation pages for each equivalence set and the qualitative severity rating.

Terminology corrections:

• Fixed terminology in code and test comments from "Equivalency Set" to "Equivalence Set" for consistency with CVSS v4 documentation. (qualitative_severity.py, _v4expected.py) [1] [2]