Add all remaining hardcoded colors to the `Color` struct

[stackotter]

SwiftUI's Color struct has a multitude of hardcoded colors available as static properties. It would be great for compatibility to add the rest of these colors to SwiftCrossUI's corresponding Color struct. As a bonus, it'd be nice to have an equivalent to SwiftUI's opacity method for easily creating variants of a color with different opacities without mutation.

[stackotter]

Completed by @jxhug