@robinloeffel do you have any reservations against this PR? Without it, I'm unable to fully adopt v9, since floydspace/serverless-esbuild#498 prevents me from using ESM for my esbuild config

Hey man! In the meantime, I went ahead and implemented your suggestions myself. With your proposed changes, the ESLint setup of the repo wouldn't have functioned anymore, since it requires a base tsconfig.json where it can derive some info for type-checking and such. Thank you for the effort you put in, I hope version 0.3.11 fixes your issues!

I really appreciate how responsive you've been so far Robin, and I hope I'm not coming across as "a bit much" with all the back-and-forth, issue creation, and so on. There's just one minor tweak that is needed for this particular problem to be fully resolved:

// package.json
{
  // ...
  "exports": {
    // ...
    "require": "./dist/cjs/index.cjs"
  },
  "main": "./dist/cjs/index.cjs",
  // ...
  "scripts": {
    // ...
    "build:cjs": "tsc --project tsconfig.cjs.json && mv dist/cjs/index.js dist/cjs/index.cjs"
    // ...
  }
  // ...
}

which resolves this error

Error [ERR_REQUIRE_ESM]: require() of ES Module
[my monorepo]/packages/api/node_modules/esbuild-plugin-eslint/dist/cjs/index.js
from [my monorepo]/packages/api/esbuild.config.cjs not supported.

index.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains
"type": "module" which declares all .js files in that package scope as ES modules.

Instead either rename index.js to end in .cjs, change the requiring code to use dynamic import() which is
available in all CommonJS modules, or change "type": "module" to "type": "commonjs" in
[my monorepo]/packages/api/node_modules/esbuild-plugin-eslint/package.json to treat all .js files as
CommonJS (using .mjs for all ES modules instead).

Don't worry about it, I'll just do it at my own pace! Should be all good now with the latest version.