Add support for SwiftUI `Color`

[hank121314]

Summary

Fixes: #78. Create a ColorBridge to support the serialization for SwiftUI Color. Color will serialize into Data with NSColor(in iOS UIColor) bridge.

Usage

extension Defaults.Keys {
    static let color = Key<Color>("swiftui_color", default: .black)
}

struct Example: View {
    @Default(.color) var color

    var body: some View {
      ColorPicker("", selection: $color, supportsOpacity: false)
    }
}

Thanks for your code review 😄 !

[hank121314]

// @L1cardo Could you help me to test this PR to make sure it fits your requirement? Thanks!

[L1cardo]

// @L1cardo Could you help me to test this PR to make sure it fits your requirement? Thanks!

Yeah, sure! I will let you know when I am done.

[L1cardo]

@hank121314 Works perfect in my case!!!