Drag windows in multitasking view in between workspaces

[danirabbit]

Problem

I think this is the last feature we missed from the old multitasking view. Sometimes you want to drag a window to create a new workspace in between existing workspace items

Proposal

Accept drags of windows in between existing workspaces in the workspace switcher. Making sure not to recreate #504

Prior Art (Optional)

Old workspace switcher :)