ESM support for config file

[trusktr]

https://github.com/jtenner/as-pect/blob/4736a6aeb4ddad677d1258133686e3a290e88ce2/packages/cli/src/run.ts#L158

Would be nice to either call require or import there based on some conditions. I haven't implemented something for that before, but I imagine this:

• if the config ends with .cjs, use require
• if it ends with .mjs, use import
• for plain .js,
  • If asp is running in a project with type:module, then use import
  • If asp is not running in a project with type:module, use require

[trusktr]

An alternative could be to allow aspect's config file to export a promise or an async function, then even if it is CJS the user can still await import() for anything and use ESM in their dependency tree that the config imports.

[jtenner]

@willemneal this is a great idea. WDYT?

[jtenner]

I think we should keep as-pect as it is until the CLI rewrite.