Support for custom and forward function.

[ciscoheat]

A small fix for supporting custom schemas, just a passthrough since they cannot be transformed to JSON schema.

[gcornut]

I'm thinking it might be better to add an option to ignore unsupported valibot validations. Some user might try to convert to JSON schema without even thinking of the fact they have custom validation that can't be converted.

[ciscoheat]

Sounds good, should I add an option like that for only custom validations, or more general?

[gcornut]

I'd say an option to ignore all unknown validations (like ignoreUnknownValidation?: boolean).
That way it could be changed later with an array of string to specifically list the validations to ignore but I don't know if it is useful

[ciscoheat]

Updated with that option now!