feat: support comments in JSON

[JustinBeckwith]

Fixes #442

[pastelmind]

Is there a way I can assist this get merged?

GitHub says that a test has failed. Unfortunately, the logs have expired, so we don't know what the problem was.

[JustinBeckwith]

This is the weirdest thing. The tests always pass locally. They fail sporadically, not dependent on node version, in GitHub Actions with the error:

 1) clean
       should avoid deleting .:
     Uncaught AssertionError [ERR_ASSERTION]: The input did not match the regular expression /Unable to parse/. Input:

'Error: Error: /tmp/tmp-3007FygcrcB0qcvm/tsconfig.json\n' +
  "ENOENT: no such file or directory, open '/tmp/tmp-3007FygcrcB0qcvm/tsconfig.json'"

@pastelmind if you're interested, you could always fork the repo, checkout this branch into your own fork, and then submit a PR to try and figure things out :) Just make sure to retry the tests a few times, because the error seems to be flaky.

[JustinBeckwith]

After closer inspection.... I forgot to await a promise 🙈 @bcoe whenever you're around, this could use a gander.

[bcoe]

@JustinBeckwith apologies for dropping this review on the ground, mind cleaning up the package-lock.json conflict, and we can work on landing.

[bcoe]

I think that these assertions should be async too? () => { to async () => {

[JustinBeckwith]

Nope! They return a promise, since withFixtures returns a promise, which seems to be what mocha is actually looking for. All the tests in this file seem to work like that 🤷