[DOC-02] Add documentation on the Taxonomy file

[aoustry]

Type of Change

New content

Description

We should now better present the Taxonomy concept.

Affected Documentation Sections

• File structure
• Core Concepts
• User Guide

Process Checklist

Step 1 — Issue Creation

• Issue created and linked to process DOC-02

Step 2 — Triage

• Process confirmed applicable
• Assigned to responsible contributor
• Priority and milestone set (if applicable)

Step 3 — Impact Analysis

• Affected documentation sections identified
• Inconsistencies between documentation and existing implementation identified
• Assessed whether change affects the GEMS Language definition (or is purely editorial/structural)
• No undocumented behavior will be introduced

Step 4 — Implementation

• Documentation pages updated
• Internal links verified
• No inconsistency introduced between documentation and implementation

Step 5 — Testing & Validation

• All documentation examples validated (no broken or incorrect examples)

Step 6 — CI Validation

• Documentation build passes (mkdocs build) without warnings

Step 7 — Review & Merge

• PR reviewed alongside documentation changes

Step 8 — Versioning ⚠️ patch bump only (or none for purely editorial changes)

• If purely editorial/structural: no version bump required; if language clarification: a documentation patch release is expected

Step 9 — Supporting Files

• If language clarification: release notes entry added (doc/0_Home/4_release_notes.md)
• AGENTS.md reviewed for impact and updated if needed

Step 10 — Release

• If a release is needed: follow the release process in the Developer Guidelines