Add option to provide coercion

[asross]

I'm generating a zod object from an openapi schema, and I'd like it to be able to coerce values, e.g. converting strings to numbers. It would be easy if I was able to edit the zod object directly, but the schema gets updated periodically, and I want to be able to automatically pull in changes without having to reproduce my edits.

How easy would it be to implement this feature?

[amvFrontendMonkey]

@astahmer I'd be willing to provide a PR for opt-in coercion

Is this something you'd accept?