LockScreen : avoid removing from composition the LoggedInFlowNode.Children when LockScreen is displayed.

features/lockscreen/api/src/main/kotlin/io/element/android/features/lockscreen/api/LockScreenService.kt

@@ -44,6 +44,12 @@ interface LockScreenService {
     fun isPinSetup(): Flow<Boolean>
 }
 
+/**
+ * Check if the app is currently locked.
+ */
+val LockScreenService.isLocked: Boolean
+    get() = lockState.value == LockScreenLockState.Locked
+
 /**
  * Makes sure the secure flag is set on the activity if the pin is setup.
  * @param activity the activity to set the flag on.