[android] - add offline troubleshooting link to javadoc of OfflineManager

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/offline/OfflineManager.java

@@ -26,7 +26,11 @@ import java.nio.channels.FileChannel;
 
 /**
  * The offline manager is the main entry point for offline-related functionality.
+ * <p>
  * It'll help you list and create offline regions.
+ * </p>
+ * 
+ * @see <a href="https://docs.mapbox.com/help/troubleshooting/mobile-offline/">Offline Maps Information/</a>
  */
 public class OfflineManager {