update the demo to show vertical spacing in grid
update the demo to show vertical spacing in grid

hachidorii/JNWCollectionView,danielmartinprieto/JNWCollectionView,konstantinpavlikhin/JNWCollectionView,Spark-Xl/JNWCollectionView,Deadpikle/JNWCollectionView,kettch/JNWCollectionView,regexident/JNWCollectionView,jwilling/JNWCollectionView