feat: allow ctx.addIssue from transform

[morgs32]

Closes out part of #696 . Except only on transforms!

z
    .string()
    .transform((data, ctx) => {
      const i = strs.indexOf(data)
      if (i === -1) {
        ctx.addIssue({
          code: 'custom',
          message: `${data} is not one of our allowed strings`,
        })
      }
      return data.length
    })
    .parse("asdf");

Will throw. ctx works just like in superRefine()

[FlorianWendelborn]

I think it would be better if this test could check for the kind of error, ideally the custom code/message.

Otherwise, this test would also pass if ctx is undefined as it would throw a JS error

[morgs32]

Good call. Checking the whole error message now.

[morgs32]

@FlorianWendelborn whaddya think? This a break from anyone's philosophy on zod? I'd love to wax zod philosophy

[FlorianWendelborn]

Well, I'm in favor of this. I don't have the power to merge anything here though, just a zod user who likes to contribute a bit with suggestions

[morgs32]

[colinhacks]

Sorry for the delay on this. Fantastic PR. Landed in 3.15.0.