convert to esm

[jtoar]

I'm still working through a few things.

The motivation for tackling @redwoodjs/project-config first was 1) most of our other package's depend on it 2) it's small 3) it would make merging the PR that converts the CLI's Jest tests to Vitest easier because Vitest can't mock require (see redwoodjs/redwood#9863).

I used arethetypeswrong/cli extensively. Right now I'm deeming the "Masquerading as ESM" error it emits acceptable. The code between the ESM and CJS files doesn't differ in functionality, only syntax; shipping two declaration copies of all the declaration files is shipping extra code. Mark Erikson did something similar at first at least here:

Unfortunately, no build tool that I knew of at that time did this by default, and the idea of shipping 99%-duplicate typedefs bothered me. So, I opted to not try to fix this "FalseCJS" issue for our packages (at least for the time being).

(Source: https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/#typescript-declarations.)

Note that FalseCJS's fancier name is "Masquerading as CJS". We have "Masquerading as ESM", not CJS. I'm not sure if it's an issue that it's flipped yet.

$ attw ./redwoodjs-project-config.tgz 

@redwoodjs/project-config v6.0.7

Build tools:
- [email protected]
- [email protected]

👺 Import resolved to an ESM type declaration file, but a CommonJS JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseESM.md


┌───────────────────┬─────────────────────────────┐
│                   │ "@redwoodjs/project-config" │
├───────────────────┼─────────────────────────────┤
│ node10            │ 🟢                          │
├───────────────────┼─────────────────────────────┤
│ node16 (from CJS) │ 👺 Masquerading as ESM      │
├───────────────────┼─────────────────────────────┤
│ node16 (from ESM) │ 🟢 (ESM)                    │
├───────────────────┼─────────────────────────────┤
│ bundler           │ 🟢                          │
└───────────────────┴─────────────────────────────┘

Regarding the .js extension in TS code, see redwoodjs/redwood#8456.