Summary:
Lets try using `UICollectionViewCompositionalLayout` with IGListKit! It does require some data plumbing, but maybe we can make that simpler in the future. For now, lets keep things simple and see how it feels.
This diff replicates the `MixedDataViewController` example starting with the expandable text.
Differential Revision: D52260529
fbshipit-source-id: 5579b8d6fe5d1f95ed282f821e6555a6a56b1c1c
