Add scrollbar to the room selector

Hi ! I use a wacom tablet as a mouse for health reasons (and also because I work as an illustrator), and those don't have a scroll wheel. They do have a standin "knob" but it's not great : I have to let go of the pen an reach out for it.

Anyway, to alleviate that I would love for you guys to add a scrollbar for this particular region (not sure how it's called, the column to the far left with the big icons).

Cheers !

Hadrien