Generate both CommonJS and ES modules

[cbenz]

Related to #175

Based on this article: https://blog.logrocket.com/publishing-node-modules-typescript-es-modules/

I added a new tsconfig file to generate a new ESM bundle. I changed the output directory from lib/src to lib/{cjs,esm}/src. I added a command to npm run build (that could have been parallelized with concurrently but maybe it's overkill).

I tested npm run build and the ES modules worked with npm link from a local application that uses ES modules with Snowpack (and I confirm that the CommonJS build did not work because of some error with those generated lines: Object.defineProperty(exports, "__esModule", { value: true });).

Obviously I did not tested npm publish, so I hope I did not break the publication process.

Note: I did not understand the need to include tsconfig.package.json in the lib/src directory, so I kept it as-is in the lib/{cjs,esm}/src directories.

[colinhacks]

Thanks for this wonderful PR! I made some small changes overriding and cleaned up all the tsconfigs — there were several redundant settings. Hopefully I didn't break anything.

Turns out there's no reason why the tsconfig.package.json was getting copied into the lib directory 🤷‍♂️ So I got rid of that.

npm publish worked fine. Please me know if the ESM module is working as expected! Once I get confirmation, I'll update the README.

Is there any specific instructions for how to consume the ES6 module? Do you have to use import * as z from 'zod/lib/esm'? Or does it work automatically in a system that supports ES6 modules?

[cbenz]

I can confirm that it worked for me now, doing import * as z from "zod". No need to reference zod/lib/esm thanks to the "module": "./lib/esm/src" key in package.json.

[colinhacks]

Excellent! Thanks Christophe!