Empty hyperlinks with a title do not cause a failure to be reported #292

Hyperlinks with no content or child nodes but with a meaningful title attribute do not pass WCAG2.1 2.4.4, since the title attribute alone does not constitute a sufficient method for complying with the standard.

Technique H33 talks about supplementing with a title rather than relying on a title alone.

Testing a link like this: <a href="https://github.com/proxy/www.github.com/" title="Visit GitHub"></a> with HTML_CodeSniffer does not report a failure and it should.

Other testing tools like WAVE do report this as a failure.

I'd be happy to try and take a look at it if you agree. It would be my first contrib!