Merge pull request #60 from amardeshbd/update-readme

[UPDATE] Readme with official project link

Author: hossain-khan

README.md

@@ -9,6 +9,13 @@ A demo application for Android `ConstraintLayout` with various usage with sample
 Get the **beta** release with current snapshot!  
 [![google-play-badge](https://user-images.githubusercontent.com/99822/40590807-b714614a-61d3-11e8-9fab-a6781bc670c2.png)](https://play.google.com/store/apps/details?id=com.hossainkhan.android.constraintlayout)
 
+## :bookmark: Official Demo
+Google has official demo project that contains a list of layouts that showcases the various features and usage of
+[ConstraintLayout](https://developer.android.com/reference/android/support/constraint/ConstraintLayout.html) and 
+[MotionLayout](https://developer.android.com/reference/android/support/constraint/motion/MotionLayout)
+
+See https://github.com/googlesamples/android-ConstraintLayoutExamples
+
 ## Proposed App Features
 * Have a grid containing different feature set of `ConstraintLayout`
 * For each feature, have different examples