`type: "module"` support

[Windvis]

Split off from #38 to have the discussion without specific implementation details.

The js template currently transpiles the code to CJS, so we can't easily import ESM modules (in a sync way) in our services. This can become an issue since there are npm packages out there that only publish ESM code now. Since we already write ESM-like code, (or TS) it might be worthwhile to change the setup to output ESM instead.

Some caveats mentioned in #38:

• node requires that local imports in ESM modules have extensions. This is breaking change since services would have to adjust the import paths. A workaround could be to use the mentioned babel plugin, but I'm not sure if we should.

[Windvis]

Someone posted this in the Ember Discord: https://joyeecheung.github.io/blog/2024/03/18/require-esm-in-node-js/

So it seems that the main reason why we wanted this change (cjs can't sync import esm) will not be an issue anymore in the future. I do still think it's a better setup though, especially since we already write ESM-ish code anyways.

[madnificent]

How does the extension work with respect to transpiling coffeescript and typescript code? Does the extension "stick" to the original extension or does everything need a .js postfix?

[Windvis]

It needs to be .js in the transpiled file, yes. I'm not 100% sure what that means in practice for the template here.