Sort sidebar menu

https://eclipse.dev/rcptt/userguide/getstarted/ should be a first page in User Guide.

Current menu order is haphazard:
<img width="389" alt="Screenshot 2025-01-10 at 19 15 12" src="https://github.com/user-attachments/assets/9bed49eb-06eb-4e67-aed7-f58ae1a11693" />


