Middle-click to open in foreground

[LeoBeliik]

from #261

I would actually love a toggle in the config for that, I understand everyone's workflow may differ, for me if I'm opening a new tab is because I want to do something in that folder so having it on focus would be desirable.
Furthermore, Dolphin (I don't know if it's the case in Nautilus), let's you auto focus to the new tab by using Shift + Middle click, right now Cosmic Files doesn't have this option (it just select folders like if you were using shift right click).
The desirable feature here would be to have a toggle in the app config to change if you want new tabs to auto focus or not, and shift + middle click would do the opposite.

Thanks!