adapter-vercel - `isr` config does not respect undefined `allowQuery` value

Describe the bug

The jsdoc for config.isr.allowQuery suggests that leaving it undefined will allow all query parameters to be cached independently. This matches up with Vercel's documentation.

However, leaving it undefined makes it so that all query parameters are ignored. This is because the adapter code sets the output allowQuery to always cache the query param '__pathname' on this line.

Because of this, there is currently no way to allow all query parameters to be cached independently.

There are multiple potential solutions:

• Add ability to set allowQuery: "*" or similar configuration
  • Pro - no breaking change
  • Con - adapter config will have different behavior than vercel docs
• Fix jsdoc to match current behavior
  • Pro - no breaking change
  • Con - unable to allow all query params
• Fix behavior to match vercel docs
  • Pro - behavior will stay in line with vercel docs
  • Con - likely a breaking change as default behavior will change

Reproduction

https://github.com/mass8326/sveltekit-isr-allow-query-issue
https://sveltekit-isr-allow-query-issue.vercel.app/?hello=world

Logs

No response

System Info

N/A

Severity

serious, but I can work around it

Additional Information

No response

Inspect packages/adapter-vercel/index.js around line 194 and the config documentation in packages/adapter-vercel/index.d.ts around lines 54-57. Reproduce the behavior with the linked example, then establish which undefined allowQuery semantics should be supported; done means the chosen behavior, implementation, and documentation agree.