Fix updating stack config props. (#231)

When some of config props change or new header items are added we need to perform a header update. This diff adds logic to trigger updating header props when that happens.

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfigViewManager.java

@@ -52,6 +52,12 @@ public class ScreenStackHeaderConfigViewManager extends ViewGroupManager<ScreenS
     return true;
   }
 
+  @Override
+  protected void onAfterUpdateTransaction(ScreenStackHeaderConfig parent) {
+    super.onAfterUpdateTransaction(parent);
+    parent.onUpdate();
+  }
+
   @ReactProp(name = "title")
   public void setTitle(ScreenStackHeaderConfig config, String title) {
     config.setTitle(title);