UI tweak: highlight task in hierarchy when its details are being viewed in the right panel

[elimisteve]

If the user is (1) viewing the task hierarchy, (2) rightPanel.tab === 'TaskDetails', and (3) rightPanel.show === true, highlight the corresponding task in the hierarchy as if it's being hovered over (should be able to use that same CSS class, or create a new one with a more appropriate name that has the same CSS rules).

@4xdk Want to work on this after 🎉 and finishing task description editing?

[4xdk]

@elimisteve Sure! Now that's what I call a healthy pipeline 😀