Add documentation links to LSP CEL hover

[stefanvanburen]

Similar to how we add links for protobuf hover docs to <protobuf.com> or <buf.build>, this adds relevant links for the various CEL functions/operators/etc. to <celbyexample.com> or <protovalidate.com>.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Mar 11, 2026, 4:41 PM

[stefanvanburen]

Double-checked these links with lychee, the one failure is just an unrelated test link:

$ lychee private/buf/buflsp/hover_cel_test.go
39/39 ━━━━━━━━━━━━━━━━━━━━ Finished extracting links                                                                                                                                                                                        [WARN] lychee detected 1 redirect. You might want to consider replacing redirecting URLs with the resolved URLs. Run lychee in verbose mode (-v/--verbose) to see details about the redirections.
Issues found in 1 input. Find details below.

[private/buf/buflsp/hover_cel_test.go]:
     [404] https://issuer.cel.dev/ | Rejected status code: 404 Not Found (configurable with "accept" option)

🔍 39 Total (in 1s) ✅ 31 OK 🚫 1 Error 👻 6 Excluded 🔀 1 Redirects

[stefanvanburen]

In VS Code: