15.0.0-alpha.1

This is an early-release version of Moya 15. This includes minimum Swift version bump to 5.1 as well as bringing back Combine support!
It's an alpha release since there might be slight breaking changes to the Combine extensions if we find some problems and also there might be improvements that are waiting in PRs.

Thanks to @MaxDesiatov @BasThomas @LucianoPAlmeida @amaurydavid and everyone else that helped in the newest release! 🚀

Changelog

Added

• We brought back Combine support! #2024 by @MaxDesiatov.

Changed

• Moya's minimum Swift version is now Swift 5.1. #1931 by @BasThomas.