added multiple monitor support

[jard285]

Added support for multiple monitors. This allows users to extend their spaces across two or more monitors so they do not need to focus the monitor before switching to the desired space

[LoLei]

I've been looking for multi monitor support, thanks!

How does this work together with the "Mission Control > Displays have separate Spaces" setting?

Without this extension, my workflow with multiple monitors, with this setting enabled, works as such:

• My primary monitor can switch Spaces via one of the shortcuts ("Mission Control > Switch to Desktop N")
• The Space on the second monitor stays fixed
• If I focus on a window on the second monitor, I can still switch Spaces on the primary monitor with one of the shortcuts ("Mission Control > Switch to Desktop N")

This currently does not work with InstantSpaceSwitcher:

• If I focus on a window on the second monitor, I can still switch Spaces on the primary monitor with one of the shortcuts ("Mission Control > Switch to Desktop N")

With InstantSpaceSwitcher, if I focus on a window on the second monitor, I cannot switch Spaces on the primary monitor with one of the shortcuts. ("Mission Control > Switch to Desktop N")

Does this PR fix this use case as well?