fix android rooBackgroundImage support (#3089)

android/app/src/main/java/com/reactnativenavigation/params/parsers/StyleParamsParser.java

         result.topTabsHeight = getInt("topTabsHeight", getDefaultTopTabsHeight());
 
         result.screenBackgroundColor = getColor("screenBackgroundColor", getDefaultScreenBackgroundColor());
+        result.rootBackgroundImageName = params.getString("rootBackgroundImageName");
 
         result.bottomTabsInitialIndex = getInt("initialTabIndex", 0);
         result.bottomTabsHidden = getBoolean("bottomTabsHidden", getDefaultBottomTabsHidden());