NonEmpty + Swift-Collections (OrderedSet, Deque...)

[iDmitriyy]

Hi

What about adding support of swift-collections to NonEmpty?
I suppose doing it with an overlay SPM module 'NonEmpty+UpcomingCollections'.

Currently, it is not possible to express NonEmpty<OrderedDictionary>, because OrderedDictionary doesn't conform to Collection protocol.
Another one problem with different Types of Dictionaries is impossibility to write generic Dictionary code. As a workaround, I've made NonEmptyOrderedDictionary implementation and added DictionaryUnifyingProtocol making possible common Dictionary operations in generic code with: Swift.Dictionary, OrderedDictionary, NonEmptyDictionary, NonEmptyOrderedDictionary. There are also TreeDictionary, SortedDictionary.
DictionaryUnifyingProtocol is something like _DictionaryProtocol in NonEmpty library with some differences.

With Set, OrderedSet, SortedSet, SparseSet + NonEmpty the approach is similar. For example, OrderedSet doesn't conform to SetAlgebraProtocol.

I can share code or make WIP pull request, but not sure how it is better to do.