feat: Add Docker Desktop Extension to quickstart guide

[westbrook-ai]

Adds the Docker Desktop Extension as an option in the Quick Start guide.

The reason other tabs beneath Docker are renamed is because the formatting turns into a mess if we don't:

[pr-validator-bot]

ℹ️ INFO

Please ensure you're targeting the correct branch:

• dev branch: For changes related to upcoming Open WebUI releases (new features, new environment variables, anything dependent on unreleased versions)
• main branch: For content that can go live immediately (fixes, tutorials, documentation not dependent on unreleased features)

Please adjust your PR target branch accordingly if needed.

[tjbck]

LGTM, Thanks!