Provide additional linters to check for accessibility features

[foosbar]

Bootstrap does a nice job documenting the places where aria-* and role attributes should be used. I'd also like to validate those with bootlint. I've been working on implementing these as an extension to bootlint, but if there's value in adding them directly into bootlint, I'd be happy to share.

[zacechola]

Even though I'm fully behind the idea of automatically doing this, I'm not sure bootlint itself is a good candidate to automate those sorts of checks.

The main purpose of bootlint is to root out common mistakes in markup structure, which won't be affected by ARIA.

There are other tools out there that do automated accessibility checking, including some open source ones that play nicely with Grunt, such as arialinter.

[mdo]

Would love a tool to track our the quality of our accessibility features.

[foosbar]

It may not be a general accessibility check like arialinter, but making it part of bootlint would make sense since certain aria attributes are associated with the bootstrap class semantics.

[cvrebert]

I'm not opposed in principle, so long as it's Bootstrap-specific. Though Bootstrap v4 will be coming relatively soon, and one of the goals there is to add some JavaScript that will add many (though probably not all) of the relevant aria-* & role attributes automatically, making this less of an issue.

[foosbar]

I committed some changes to my branch. Would love some feedback on the direction, but it's not ready for PR yet as some of the existing tests are broken.

I am thinking of either making the accessibility checks warnings or making it an optional check.

[foosbar]

I love that Bootstrap 4 will add those in automatically. This will let us validate some of the localized attributes like aria-label.