[Cin] emulation of middle mouse button via xinput

Because I also run cin on laptop (for now) I found this info useful https://dev.to/bramaudi/enabling-mouse-middle-click-emulation-in-linux-23nb also, if you accidently try to capture too big area (for example 1600x1200 vs real 1600x900) you will get black capture window and some X errors on console...