Add default context responses to PlayPauseButton

[jessegreenberg]

From #881

It would be good to have a general context response in PlayPauseButton. Working with @terracoda, we took the one from greenhouse-effect which is general:

Subject: [PATCH] Remove custom focus management for the home screen buttons, focus should start at the top of the home screen like all ScreenViews, see https://github.com/phetsims/joist/issues/695
---
Index: js/buttons/PlayPauseButton.ts
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/js/buttons/PlayPauseButton.ts b/js/buttons/PlayPauseButton.ts
--- a/js/buttons/PlayPauseButton.ts	(revision 2440ab76884e9d8ac047702e99bd6dab301d4079)
+++ b/js/buttons/PlayPauseButton.ts	(date 1730906572322)
@@ -33,7 +33,13 @@
 
       // PlayControlButtonOptions
       includeGlobalHotkey: true,
-      endPlayingLabel: SceneryPhetStrings.a11y.playControlButton.pauseStringProperty
+      endPlayingLabel: SceneryPhetStrings.a11y.playControlButton.pauseStringProperty,
+
+      // An alert that is spoken when the sim is paused.
+      pausedContextResponse: 'Sim paused. Play to continue exploration.',
+
+      // An alert that is spoken when the sim resumes playing. Fill in with sim specific information.
+      playingContextResponse: ''
     }, providedOptions );
 
     // icon sized relative to the radius