Add support for ZodPipeline and ZodDiscriminatedUnion

[KTGLeiden]

We noticed during testing that support for ZodPipeline and ZodDiscriminatedUnion was missing, something that will break if you use something like:

export const PostalCodeSchema = z
  .string()
  .transform((postalCode: string) => postalCode.toUpperCase().replaceAll(' ', ''))
  .pipe(z.string().regex(/^\d{4}(?:[A-Z]{2}|\d)?$/, 'Invalid postal code'))

Or:

export const SomeDiscriminatedUnion = z
  .discriminatedUnion('type', [
    SchemaAWithType,
    SchemaBWithType,
    SchemaCWithType,
  ])

As a DiscriminatedUnion is basically a union for the purpose of this lib I opted for the same response.
for the ZodPipeline case, I opted for the output type.

[matejchalk]

LGTM 👍 Thanks for you contribution 🙂