How do I specify the server URL in openapi.json?

https://cloudflare.github.io/itty-router-openapi/user-guide/router-options/

I thought `OpenAPIRouter` supports specifying the server URL so that the generated `openapi.json` will have the server URL info, but I can't find the option in the doc linked above. Is this feature supported?

Start with the linked router options guide and the OpenAPIRouter configuration entry point. Check whether the generated openapi.json currently supports a server URL and whether the option is documented there. Done means the supported behavior and configuration path are clear, or the missing feature's scope is defined.

Written by the indexing model from the issue text.