Separate display_change into more specific events

[Masstronaut]

I use aerospace and have sketchybar setup to display which workspaces & windows are on each display. Specifically, the sketchybar item for a workspace is only rendered on the monitor that the workspace is assigned to by aerospace.

When a display is disconnected (ie undocking my laptop) sketchybar doesn't know how to update the rendering of items assigned to the disconnected display, so they aren't rendered. It would be great to get an event like display_removed sent to every item assigned to a display that is no longer connected. That would make it easy to efficiently handle the event.

More broadly, I think it would be great to have more specific events like:

• display_added
• display_removed
• display_moved
• display_resized

While perusing the sketchybar source to see how viable that would be, it looks like the events are already identified and plumbed, but they all emit the same display_change event without sufficient info to know how I should handle it (was it just the focused display changed? did one get added or remove? I have no idea!)

@FelixKratz would you be open to a PR that splits these out into separate events (breaking change) or a purely additive approach that continues to emit display_change and additionally emits a more specific event?