Fix caching in Cloudflare router for static/SSR sites

[mlafeldt]

HEAD or POST requests currently result in this exception:

{
  "stack": "    at saveCache (worker.mjs:71:19)\n    at respond (worker.mjs:85:13)\n    at fetch (worker.mjs:35:22)",
  "name": "TypeError",
  "message": "Cannot cache response to non-GET request.",
  "timestamp": 1722691361303
}

Fixes #842

[jayair]

Can you open an issue for this? I'll assign it to have it reviewed.

[mlafeldt]

Can you open an issue for this? I'll assign it to have it reviewed.

You can also assign PRs. :) But yeah, here it is: sst/sst#4294

[fwang]

Thanks @mlafeldt!