message: Fixed the version number of the NDK in the README.md file
diff: @@ -6,7 +6,7 @@ This demo project is for the Alice on Android simulator or actual devices. You c
  It requires the Android Studio 3.6 or newer
  #### NDK
  -Open the demo project and install the NDK (Side by side) version 20.0.5594570 using Android Studio
  +Open the demo project and install the NDK (Side by side) version 21.1.6352462 using Android Studio
  ```
  Tools -> SDK Manager -> SDK Tools -> Check 'Show Package Details' -> Install the NDK (Side by side) version 21.1.6352462
  ```
  