Check fragments in HTML files

[HU90m]

Part of the #185 work.

This PR adds fragment checking for the second type of link in #185 (comment) .

[mre]

Looks really nice. Especially the refactoring in fragment_checker.
I've added some comments.
Are you planning to add support in html5ever as well?

[HU90m]

Are you planning to add support in html5ever as well?

What would be the benefit of doing this?

[mre]

The main advantage would be feature-parity with html5gum. Then again, we wanted to remove html5ever anyway at some point and it shouldn't be a blocker. Just checking if the PR is done and ready for review.

[HU90m]

The main advantage would be feature-parity with html5gum. Then again, we wanted to remove html5ever anyway at some point and it shouldn't be a blocker. Just checking if the PR is done and ready for review.

Ah cool, yeah I hadn't created a html5ever version because it looked like html5ever was being depreciated (and it routing the html5ever option into the file checker seemed like additional unnecessary work).

[mre]

At long last, I finally came around to reviewing and merging this. Apologies for the delay. The feature turned out great! Thanks for the contribution (and your patience) @HU90m. 🤩

[HU90m]

No apology needed. Thanks for making it so easy to contribute!