Set visibility on flashButton to be public

This changes the visibility of the flash button to public so that you
can change its location or hide it.

Author: zenangst

Sources/BarcodeScannerController.swift

@@ -42,10 +42,9 @@ open class BarcodeScannerController: UIViewController {
   lazy var infoView: InfoView = InfoView()
 
   /// Button to change torch mode.
-  lazy var flashButton: UIButton = { [unowned self] in
+  public lazy var flashButton: UIButton = { [unowned self] in
     let button = UIButton(type: .custom)
     button.addTarget(self, action: #selector(flashButtonDidPress), for: .touchUpInside)
-
     return button
     }()