Provide an alternative mechanism for checking ZodType in parsers

[ghost]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Issue

This original issue - #12

Testing Remix Loaders with Vitest sometimes produces the following error:

TypeError: keyValidator._parse is not a function

The issue appears to be a result of using instanceof to check an object is of a ZodType class. However, during a Vitest build this class is duplicated, meaning instanceof is performed against a unrelated class. (An explanation of this can be found in the comments for the original issue).

Proposal

This PR implements the proposed solution from @taternz #12 (comment), providing an alternative way to check for an object is an instance of the ZodType class.

Obviously this is only a very superficial check to see that the object we receive contains a parse method. An alternative could be to do a shallow comparison of the Object.keys to determine object equality?

[rileytomasek]

Thanks for the PR and sorry for the slow response. While not ideal, I'm ok with this approach if you also check safeParse, safeParseAsync, and parseAsync for completeness. If you update the PR I'll merge and cut a new release.