Test Babel 8 compatibility

[nicolo-ribaudo]

Hey, Babel has an e2e test for Ember which makes me realize that this package cannot seamlessly upgrade to Babel 8.

• The first commit updates the code to still use Babel 7, but in a way that will also work with Babel 8
• The second commit updates the test runner to run, when using modern Node.js versions, as native ESM rather than transpiling through Jest. Without this, it won't be possible to upgrade to Babel 8 because it's written in ESM and Jest has problems with it.
• The third commit adds a CI job to make sure that the codebase is compatible with Babel 8.

This PR doesn't upgrade to Babel 8 yet, but it makes sure that when Babel 8 will be stable and you'll be ready for a major release you can simply update the dependency :)

[nicolo-ribaudo]

Ping @NullVoxPopuli :)

[mansona]

I don't know why CI isn't running on this one 🤔 and github isn't giving me the option to approve anything. I wonder if it's because you edited the ci.yml and it's not happy 😞

Could you open a PR with just your first commit and I can get that merged and then you won't need approval anymore for CI?

[nicolo-ribaudo]

Rebased, and CI is now running :)

[mansona]

Yay CI is running! ... and failing 🫠

I am going to release the other change since that's compatible and this is just an internal testing change now. Maybe you have nerd sniped @NullVoxPopuli to get it over the line 😉

[NullVoxPopuli]

It's a ts compat issue -- like, our internal TS version is too old for file extensions.

so, I think we should drop support for TS so old they don't believe in file extensions lol
(separate PR tho)

[nicolo-ribaudo]

It's only for tests, I can also remove that option and ts-ignore the import.

[nicolo-ribaudo]

Oh well that didn't actually work, I'm debugging this locally

[NullVoxPopuli]

Seems good