Backport of UICollectionViewCompositionalLayout to earlier iOS 12
Fix different behavior with above iOS 13 when set UIScrollViewContentInsetAdjustmentNever https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/pull/150
Fix crash for recursive call on setCollectionViewLayout(_:animated:) https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/issues/129 https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/pull/149
Partially fix calculating estimated size. Fix an issue that a layout group's content insets are not honored. Fix supplementary view does not anchor with estimated sized cells.
Fix a crash on orthogonal sections using a background view.
Automatically promoted section items' zIndex to 1 if the section has decoration items.
Make inter-item spacing between groups calculated correctly.
Add support for layout item edge spacing. Add support for estimated size with edge spacing.
Fix inter-section spacing calculation. Performance improvement for orthogonal scrolling layout calculation. Supplementary items adding to decoration size. by @notjosh https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/pull/81 https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/pull/82 Fix nested collection view for orthogonal scrolling doesn't reuse cells. https://github.com/kishikawakatsumi/IBPCollectionViewCompositionalLayout/pull/74
Adding support for Swift Package Manager.
Add support for custom layout group and items.