Update Cloudflare Rust page with D1 binding and replace stale GitHub commit links

[liulk]

Existing documentation URL(s)

• https://developers.cloudflare.com/workers/languages/rust/#fetch-parameters

What changes are you suggesting?

Under the fetch parameters section:

• D1 binding is missing. Suggest linking to: https://docs.rs/worker/latest/worker/#d1
• Secret and Var are links to a GitHut commit more than 2 years ago. Suggested:
  • Secret: https://docs.rs/worker/latest/worker/struct.Secret.html
  • Var: https://docs.rs/worker/latest/worker/type.Var.html

Additional information

No response