refactor: rename 'Releases' to 'Documentatie'

Changed terminology from release notes to feature documentation
to better reflect the continuous build-in-public approach.

Changes:
- Navigation: "Releases" → "Documentatie"
- Page titles: "Release Notes" → "Feature Documentatie"
- Metadata descriptions updated
- Timeline link text updated
- Sidebar heading updated
- Template and example docs updated

The /releases route remains the same for stability,
but all user-facing text now says "Documentatie".

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/templates/release-note-template.mdx

@@ -5,7 +5,7 @@ group: "foundation | features | infrastructure"
 version: "0.1.0"
 releaseDate: "2024-11-15"
 status: "completed | in_progress | planned"
-description: "Korte beschrijving (1-2 zinnen) voor overview pagina"
+description: "Korte beschrijving (1-2 zinnen) voor documentatie overview"
 ---
 
 ## Overview