Added scroll bar on main window

[bliz937]

No description provided.

Further UI problems have occurred, investigating whether it is connected to this PR or not.

[ghost]

Actually, comparing it to master, the level of GUI brokenness [for me] has remained just about the same, the only issue is all the area being active instead of just a tab, which [I guess] will make it unavailable for screen readers, but since the GUI is already not usable with them (there is a ticket that I can't find at the time of writing this), this is acceptable as of now.

master:

Your branch:

[tatokis]

Right, since we need to get this over with.
Based on your modifications, I turned off the extra borders and removed any extra padding, however it seems to cause issues on high DPI screens.

I am not really sure how to proceed at this point.