Implement app Exposé with accessibility since the CoreDock notification broke

[nriley]

Obsoletes #1608.

[phillco]

Imports should probably be at the file module level unless it's needed to break a circular import

[phillco]

Why not something like this?

Suggested change

	def dock_app_expose():
	from pathlib import Path
	def dock_app_expose(app: Optional[App]):
	if app is None:
	app = ui.active_app()

Than a user could choose to add:

<user.running_applications> window expose user.dock_app_expose(running_applications)

I've generally taken this pattern in my own scripts rather than hardcoding ui.active_app() inside of it; it makes the action more flexible (even if we don't ship this particular grammar in community, although I think it's useful)

[nriley]

user.running_applications returns a str rather than a ui.App. But this works:

^window <user.running_applications>$:
    app = user.get_running_app(running_applications)
    user.dock_app_expose(app)

Seems OK?