Report alerts conveied by UI Automation's systemAlert event (#7282)

* Support UI Automation's systemAlert event, and provide a basic implementation that just reports the element that received the event in speech and braille, similar to focus.
Examples of where this alert is fired are Skype for Business notifications and Microsoft Edge notifications.

* Also support UIA systemAlert in braille.

source/NVDAObjects/UIA/__init__.py

@@ -1308,6 +1308,16 @@ def event_valueChange(self):
 			return
 		return super(UIA, self).event_valueChange()
 
+	def event_UIA_systemAlert(self):
+		"""
+		A base implementation for UI Automation's system Alert event.
+		This just reports the element that received the alert in speech and braille, similar to how focus is presented.
+		Skype for business toast notifications being one example.
+		"""
+		speech.speakObject(self, reason=controlTypes.REASON_FOCUS)
+		# Ideally, we wouldn't use getBrailleTextForProperties directly.
+		braille.handler.message(braille.getBrailleTextForProperties(name=self.name, role=self.role))
+
 class TreeviewItem(UIA):
 
 	def _get_value(self):

source/_UIAHandler.py

@@ -138,6 +138,7 @@
 	#UIA_AsyncContentLoadedEventId:"documentLoadComplete",
 	#UIA_ToolTipClosedEventId:"hide",
 	UIA_Window_WindowOpenedEventId:"UIA_window_windowOpen",
+	UIA_SystemAlertEventId:"UIA_systemAlert",
 }
 
 class UIAHandler(COMObject):