feat: update versioning paths and add version banners

This PR finalises versioning for the specification website:

• Simplifies paths (WIP at /docs, releases at /docs/{version})
• Adds banners for WIP, latest, maintained, and unmaintained versions
• Introduces a /versions page for clearer navigation
• Centralises version config in src/config/versions.ts

The intent is to provide clearer guidance for users and a maintainable structure going forward.

Note

The existing Disclaimer Banner will be moved to the global DocItem component and will display the appropriate message depending on the value of suitableFor within the version config for the given version.

Work in Progress Banner

Latest Released Banner

Maintained Release Banner

Unmaintained Release Banner

Version Page