webc:type="module" for simpler ESM-friendly render functions

[zachleat]

https://www.11ty.dev/docs/languages/webc/#webctyperender-(javascript-render-functions) are currently CJS but we should add another type for ESM!

[zachleat]

I’d like to feed two birds with one meal and simply call it webc:type="js" and forgo the function convention from webc:type="render" altogether.

Mentioned by @darthmall in #28. This would match how dynamic attributes work.

[zachleat]

Welp, after a bare minimum of research it looks like Node is not quite ready for vm.Module (still experimental in Node 19) https://nodejs.org/api/vm.html#class-vmmodule

Gonna have to decouple these

[zachleat]

#73 is now the request from #69 (comment)