0.21.0

• Changed: the Composable Architecture now depends on Identified Collections for IdentifiedArray, which has been rewritten for correctness and performance. There are some breaking changes, which are documented in its release.
• Changed: support for Swift 5.1 and 5.2 has been dropped. Please use Swift 5.3 (Xcode 12) or later, or this is of course a breaking change, and you must lock your application to swift-composable-architecture 0.20.0 or earlier.
• Changed: Reducer.binding now takes an extract function, not a case path. Case path expressions can still be used, meaning existing uses should generally continue to compile. If you were passing a concrete CasePath value, this is a breaking change, and you can pass along the CasePath.extract(from:) method, instead.
• Changed: TestStore has relaxed its Equatable constraint on Action. It is only required for when TestStore.receives actions from effects.
• Performance improved: view stores now perform the minimum number of equality checks necessary (thanks @iampatbrown).
• Fixed: ViewStore.publisher now emits the current store state, and not the previous state (thanks @maximkrouk, @iampatbrown).
• Infrastructure: cleaned up recursive case study, web socket case study; added benchmarking target.