Introduce ZodTransformError type, to allow for transforms that fail

[Duncan3142]

This PR introduces a new Error type, ZodTransformError, which accepts an array of issues in it's constructor.

Closes https://github.com/colinhacks/zod/issues/1390

When thrown inside a transform, this error class will be caught by Zod, and the issues it contains treated a fatal and added to the parse result.

The rational for this PR is to allow for transforms that may fail, such as the following example.

import { ZodTransformError } from "zod";

const user = z.string().transform(async (id) => {
  try {
    const user = await getUserById(id);
    return user;
  } catch (e) {
    throw new ZodTransformError([{
      code: "custom",
      message: "User not found",
    }]);
  }
});

[netlify[bot]]

✅ Deploy Preview for guileless-rolypoly-866f8a ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	94c71b53f709a2e9c7138fb2412347bf62bc7cc0
🔍 Latest deploy log	https://app.netlify.com/sites/guileless-rolypoly-866f8a/deploys/6318df910e7060000812becb
😎 Deploy Preview	https://deploy-preview-1389--guileless-rolypoly-866f8a.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[netlify[bot]]

✅ Deploy Preview for guileless-rolypoly-866f8a ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	7db2ad46ff40d8548a1f501c521f12e16149159c
🔍 Latest deploy log	https://app.netlify.com/sites/guileless-rolypoly-866f8a/deploys/6325cff7e7a39a0009070c6d
😎 Deploy Preview	https://deploy-preview-1389--guileless-rolypoly-866f8a.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[toofff]

@Duncan3142 Would you have visibility for the merge of this new feature or otherwise an alternative use with what is currently in ZOD?

[colinhacks]

Thanks for this PR! This same scenario can now be addressed with ctx.addIssue inside the .transform() method:

const user = z.string().transform(async (id, ctx) => {
  try {
    await "asdf";
    throw new Error();
  } catch (e) {
    ctx.addIssue({
      code: z.ZodIssueCode.custom,
      message: "User not found :(",
    });
  }
});

Closing for now, let me know if the new solution doesn't cover your use cases.