updated to Motion.async where DispatchQueue.main.async calls are made

Sources/Motion.swift

@@ -503,7 +503,7 @@ fileprivate extension Motion {
             if isNavigationController {
                 // When animating within navigationController, we have to dispatch later into the main queue.
                 // otherwise snapshots will be pure white. Possibly a bug with UIKit
-                DispatchQueue.main.async { [weak self] in
+                Motion.async { [weak self] in
                     self?.animate()
                 }
             } else {