feat: extend to-json-schema to add custom handlers

[MathurAditya724]

Can we add custom action handlers in toJsonSchema function? I wanna add a capability to define OpenAPI specs like ref, example, etc in the metadata action. That way I can add the custom handler to process this data and pass it in the Specs.

I am open to working on the PR for this, wanna discuss some ideas and hear your thoughts before moving forward on this.

Ref issue - rhinobase/hono-openapi#61

[fabian-hiller]

Great idea! We could also provide an official openapi metadata action. Feel free to discuss your API ideas for the custom handlers here, and once we decide on an API, you are welcome to implement it! 🚀