Empty Value Attribute Handling #75

Hi all, great package, love it so far 🚀

I'm currently struggling with one problem tho: The HTML attributes that have no specific value, actually automatically get transformed to have a value of their own key.

I think this transformation is kinda weird, especially since the current HTML standard is specifying that the value of an empty attribute is actually an empty string, not a string that matches the name of the attribute:

https://html.spec.whatwg.org/multipage/syntax.html#attributes-2

Additionally, it breaks the behavior of some JS / HTML frameworks, which is a pity. Here's a quick example without any plugins installed:

Input

<div a b c="c"></div>

Expected

<div a b c="c"></div>

Output

<div c="c" a="a" b="b" other="other"></div>

I'd also be open to contributing and fixing this if it would be appreciated.

Kind regards
Niklas