Delete swiftpm files

Make usage of `StaticBigInt` conditionally. Reduce deployment target …

…requirements down to macOS 10.13 and iOS 13.

Fix typo in README.

Support random number generation for Complex. Migrate project to Swif…

…t 5.7 and Xcode 14.

Support random number generation for BigInt.

Several enhancements of the `Complex` type. Migrated project to Swift…

… 5.4 and Xcode 12.5

Updated version numbers in library/framework.

Update documentation.

Update documentation.

Include iOS scheme in Xcode package. Clean up Xcode project.