Add test-spec-links.js linter

[queengooborg]

This PR adds a new linter to BCD, which checks the spec URLs and confirms whether they are valid based upon a W3C database as well as the statuses (non-standard and deprecated). This linter also checks for the presence of an MDN URL and alerts us when one is required.

Since there are a number of files that are in need of a spec URL being added (amongst other issues), this linter will FAIL for the time being.

Thanks to the amazing @sideshowbarker for writing the code that went into this linter! This was a joint effort to take his checker and turn it into a linter for everyone in BCD. This PR wouldn't be here without his wonderful work!

[sideshowbarker]

I would vote for making the “requires an mdn_url” case a warning case that doesn’t case a non-zero exit status. And the same for the “marked as non-standard, but has a spec_url” and “marked as deprecated, but has a spec_url” cases.

I believe the “requires a spec_url” case is th eonly case we should consider making a non-zero-exit failure case.

And further, maybe the other messages should not even be emitted by default but instead maybe only optionally — by choosing some lint-full option or something.

I say all that because the “requires a spec_url” cases are really the only ones that I think of as errors that are absolutely in need of fixing. They are gaps in the data that cause it to be missing essential information.

Therefore, I think this lint should allow those ”requires a spec_url” cases to be brought to everybody’s attention without getting overrun/obscured by the volume of the other messages.

[queengooborg]

I had similar thoughts of reworking the linter to allow for warnings. I'm planning to discuss the linters and their structure with Daniel when he gets back from his vacation!

[github-actions]

This pull request has merge conflicts that must be resolved before we can merge this.

[github-actions]

This pull request has merge conflicts that must be resolved before we can merge this.

[github-actions]

This pull request has merge conflicts that must be resolved before we can merge this.

[github-actions]

This pull request has merge conflicts that must be resolved before we can merge this.

[queengooborg]

I'm going to go ahead and close this PR because I now realize that we'll probably end up just converting the existing spec check, and the statuses are handled by #15889.