Support for :has pseudo selector

[binarytemple]

Feature goal

(From JSoup docs)

:has(selector): find elements that contain elements matching the selector; e.g. div:has(p)

input = “<div><p>foo</p><h2>$100</h2></div><div><h1>foo</h1></div>”

result = Floki.find(html, “div:has(p) > h2”)

[bvobart]

Implementing :has should also provide a solution to #592, i.e. finding the parent of a specific element. For example, to select the div that contains the h1 with text foo from your example, we could simply use the selector div:has(> h1:fl-contains('foo')).

See here for the W3C spec of CSS :has: https://www.w3.org/TR/selectors-4/#has-pseudo