Self closing non void elements validations #590
Description
Hi,
While parsing one of the error files, I noticed that the messages coming from HtmlDocument.ParseErrors are not very precise. Of course they are somewhat correct but in my opinion insufficient to quickly track down the problem which was the self closing non void element (in my case it was style element). I suggest adding a specific validation for this particular case so as to better follow the html specfication: https://html.spec.whatwg.org/multipage/syntax.html#elements-2 and properly report all self closing elements which are not void elements cited in the link above. I created simple test file which produces such results:
<html>
<head>
<title>Title here</title>
<style type="text/css" />
</head>
<body>
</div>
Some text here
</div>
</body>
</html>
I'm talking about such validation because result produced by HAP (with default options) looks like this:
<html>
<head>
<title>Title here</title>
<style type="text/css"></style></head></html>
and it might be a little hard to understand thos parsing errors if we didn't notice malformed style node in orginal document