Stop playing sounds when stopping app

LeCountdown/LeCountdownApp.swift

@@ -30,6 +30,8 @@ struct LeCountdownApp: App {
         self._registerBackgroundRefreshes()
     }
     
+    @Environment(\.scenePhase) var scenePhase
+    
     #if os(iOS)
     @Environment(\.horizontalSizeClass) private var horizontalSizeClass
     #endif
@@ -57,6 +59,14 @@ struct LeCountdownApp: App {
             .onAppear {
                 self._onAppear()
             }
+            .onChange(of: scenePhase) { newPhase in
+                switch newPhase {
+                case .inactive:
+                    Conductor.maestro.stopSoundIfPossible()
+                default:
+                    break
+                }
+            }
         }
 
     }