Create type aliases on long types

[bidoubiwa]

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Types in the library can become very long. For example:

https://github.com/meilisearch/meilisearch-swift/blob/6b3d779c726a461be1009e9786773709589627d0/Sources/MeiliSearch/Client.swift#L208

This makes for hard to read code and hard to maintain. Type aliases are a good solution to that. For example the above could become TaskResults