Mark runtime magic modules as @_implementationOnly (#48)

Author: davdroman

Sources/NavigationTransitions/NavigationTransition+UIKit.swift

@@ -1,6 +1,6 @@
 @_spi(package) import NavigationTransition
-import RuntimeAssociation
-import RuntimeSwizzling
+@_implementationOnly import RuntimeAssociation
+@_implementationOnly import RuntimeSwizzling
 import UIKit
 
 extension AnyNavigationTransition {
@@ -117,7 +117,7 @@ extension RandomAccessCollection where Index == Int {
     }
 }
 
-extension UINavigationController: RuntimeAssociation {
+extension UINavigationController {
     private var defaultDelegate: UINavigationControllerDelegate! {
         get { self[] }
         set { self[] = newValue }
@@ -251,7 +251,7 @@ extension UINavigationController {
 }
 
 @available(tvOS, unavailable)
-extension UIGestureRecognizer: RuntimeAssociation {
+extension UIGestureRecognizer {
     var strongDelegate: UIGestureRecognizerDelegate? {
         get { self[] }
         set {

Sources/RuntimeAssociation/RuntimeAssociation.swift

@@ -16,3 +16,5 @@ extension RuntimeAssociation {
         }
     }
 }
+
+extension NSObject: RuntimeAssociation {}