scroll fixes + tab hover fix

Fix hightligh on tab hover should not have the same as the active tab.
Fix spamming scroll event.
Fix scroll behavior to match this:

I think the view should scroll to the newly opened background tab, unless it would result in the active tab being hidden (this is the default behavior of Firefox). Also, like the Firefox default tab bar, I’d like a visual indication that a tab is opened down there but not visible in the view. Maybe just changing the color of the shadow from black to blue for maybe one second.

This should solve #5 (closed)