Add LHLL to CODEOWNER for in_app_purchase (flutter#2641)

Author: Chris Yang

CODEOWNERS

@@ -15,7 +15,7 @@ packages/espresso/*                           @collinjackson @adazh
 packages/google_maps_flutter/*                @cyanglaz
 packages/google_sign_in/*                     @cyanglaz @mehmetf
 packages/image_picker/*                       @cyanglaz
-packages/in_app_purchase/*                    @mklim @cyanglaz
+packages/in_app_purchase/*                    @mklim @cyanglaz @LHLL
 packages/ios_platform_images/*                @gaaclarke
 packages/package_info/*                       @cyanglaz @matthew-carroll
 packages/path_provider/*                      @matthew-carroll