Handling multiple monitors

[eLopez6]

`xrandr`.scan(/current (\d+) x (\d+)/).flatten gets the display size, which is based on the size of the multiple connected monitors.

xrandr returns useful information about XWAYLAND being connected.

Desired behavior: launching Semblance on one monitor generates a slideshow using that monitor's dimensions and not the combined resolution.

Idea:
Get the monitor running Semblance before starting the slideshow and use those dimensions.