Fix highlighting for shadowroot elements

[michael-brueggemann]

No description provided.

[PRGfx]

As far as I can tell, this merely works by coincidence, as you pop the last result, while the previous approach took the first result matching the query-selector.

However, I do think that the previous code was incorrect, as target does not describe options of selectors (as interpreted here by joining the selectors with ,) but rather describes a path in frame-access (or shadow DOM I guess). (Looking at the names of the types UnlabelledFrameSelector = CrossTreeSelector[] etc. and their introduction dequelabs/axe-core@9e1e31b.)

So I think the element would be retrieved by reducing the target something like target.reduce((root, selector) => root ? root.querySelector(selector) : null, document.documentElement) – possibly using some sort of shadow-DOM access. I didn't look into that in too much detail yet though.