SwitchWindowCommand: Also support macOS and Linux 

The file that needs to be modified is [SwitchWindowCommand.scala](https://github.com/reibitto/command-center/blob/81663de8615a67cbdf03f119a26ab8ddbd4c8925/core/src/main/scala/commandcenter/command/SwitchWindowCommand.scala#L12)

I don't know if jna-platform has all the functions necessary to make this possible for macOS and Linux. If they're not there, we'll have to add the bindings.