[Package] Added SwiftPM support and added fix to ensure the currentHandle exists event when no touch has started

The fix is required to ensure the that the brightness control works when is touched before the wheel.

Package.swift

@@ -0,0 +1,27 @@
+// swift-tools-version:5.2
+
+import PackageDescription
+
+let package = Package(
+    name: "ChromaColorPicker",
+    platforms: [
+        .iOS(.v10)
+    ],
+    products: [
+        .library(
+            name: "ChromaColorPicker",
+            targets: ["ChromaColorPicker"]
+        )
+    ],
+    targets: [
+        .target(
+            name: "ChromaColorPicker",
+            path: "Source"
+        ),
+        .testTarget(
+            name: "ChromaColorPickerTests",
+            dependencies: ["ChromaColorPicker"],
+            path: "Tests"
+        )
+    ]
+)

Source/ChromaColorPicker.swift

@@ -91,6 +91,10 @@ public class ChromaColorPicker: UIControl, ChromaControlStylable {
         handles.append(handle)
         colorWheelView.addSubview(handle)
         brightnessSlider?.trackColor = handle.color
+        
+        if currentHandle == nil {
+            currentHandle = handle
+        }
     }
     
     public func connect(_ slider: ChromaBrightnessSlider) {