docs: colors, views, and string

Sources/CoffeeUI/BackgroundView.swift

@@ -1,9 +1,14 @@
 import SwiftUI
 
+/// View with a colored background
 public struct BackgroundView<Content: View>: View {
     let color: Color
     var content: () -> Content
     
+    /// Create a View with a background color
+    /// - Parameters:
+    ///   - color: background color
+    ///   - content: view over the background color
     public init(color: Color = .background, @ViewBuilder content: @escaping () -> Content) {
         self.color = color
         self.content = content

Sources/CoffeeUI/Color+Defaults.swift

@@ -8,6 +8,7 @@
 import UIKit
 import SwiftUI
 
+/// Additional colors used by the package
 public extension Color {
     
     static var background: Color {