`crates/csslsrs/src/features/document_symbols.rs`: details banger?

<img width="496" alt="image" src="https://github.com/user-attachments/assets/637f6d68-09ad-4f0a-9851-fefcae655338" />

What if we had details on every symbols ? Not just `at_rules`, but like display the value of a property, etc.

<img width="286" alt="image" src="https://github.com/user-attachments/assets/ec0ff386-a928-4189-928a-ca757ac72b33" />

It'll help a lot for navigation too