Add the announcement of switched workspaces from Niri.

I haven't tested this with Braille support; I don't remember what I did with the cable.

internal/atspi/adapter.go

@@ -67,6 +67,7 @@ const (
 	DocumentLoadCompleteEvent  = "document:load-complete"
 	DocumentLoadStoppedEvent   = "document:load-stopped"
 	BusyStateEvent             = "object:state-changed:busy"
+	AnnouncementEvent          = "object:announcement"
 )
 
 var eventTypes = []string{
@@ -96,6 +97,7 @@ var eventTypes = []string{
 	DocumentLoadCompleteEvent,
 	DocumentLoadStoppedEvent,
 	BusyStateEvent,
+	AnnouncementEvent,
 	"object:state-changed:checked",
 	"object:state-changed:expanded",
 	"object:state-changed:indeterminate",