[Feature Request] Highlight currently selected post when navigating using keyboard shortcuts

[techno156]

When navigating via keyboard shortcuts, it can be difficult to tell what comment/post that you have selected, since there's no way to tell, other than seeing what post/comment moves up, or is affected.

One way to do this might be to highlight the current active post/comment, whether with a box around it, or by highlighting it, in much the same way that comments are highlighted when the cursor hovers above them.