Add convenient method to UIButton to set a background color as an image.

Riot/Categories/UIButton.swift

@@ -29,4 +29,15 @@ extension UIButton {
         titleLabel.numberOfLines = 0
         titleLabel.textAlignment = textAlignment
     }
+        
+    /// Set background color as an image.
+    /// Useful to automatically adjust highlighted background if `adjustsImageWhenHighlighted` property is set to true or disabled background when `adjustsImageWhenDisabled`is set to true.
+    ///
+    /// - Parameters:
+    ///   - color: The background color to set as an image.
+    ///   - state: The control state for wich to apply this color.
+    func vc_setBackgroundColor(_ color: UIColor, for state: UIControl.State) {
+        let image = UIImage.vc_image(from: color)
+        self.setBackgroundImage(image, for: state)
+    }
 }