Split into multiple packages.

Splitting into multiple packages allows users to import only the package they intend to use, which leads to smaller binary sizes. This is backwards compatible with no changes needed by end users.

For users who may not be interested in say web auth sessions, they need only `import SafariView`.

fix access control

Package.swift

@@ -6,9 +6,20 @@ let package = Package(
     name: "BetterSafariView",
     platforms: [.iOS(.v13), .macOS(.v10_15), .watchOS("6.2")],
     products: [
-        .library(name: "BetterSafariView", targets: ["BetterSafariView"])
+        .library(name: "BetterSafariView",
+                 targets: ["BetterSafariView"]),
+        .library(name: "SafariView",
+                 targets: ["SafariView"]),
+        .library(name: "WebAuthenticationSession",
+                 targets: ["WebAuthenticationSession"])
     ],
     targets: [
-        .target(name: "BetterSafariView")
+        .target(name: "BetterSafariView",
+                dependencies: ["SafariView", "WebAuthenticationSession"]),
+        .target(name: "SafariView",
+                dependencies: ["Shared"]),
+        .target(name: "WebAuthenticationSession",
+                dependencies: ["Shared"]),
+        .target(name: "Shared")
     ]
 )

Sources/BetterSafariView/BetterSafariView.swift

@@ -0,0 +1,2 @@
+@_exported import SafariView
+@_exported import WebAuthenticationSession

Sources/BetterSafariView/SafariView/SafariViewPresentationModifier.swift → Sources/SafariView/SafariViewPresentationModifier.swift

@@ -1,6 +1,7 @@
 #if os(iOS)
 
 import SwiftUI
+import Shared
 
 struct SafariViewPresentationModifier: ViewModifier {
 

Sources/BetterSafariView/Shared/UIView+viewController.swift → Sources/Shared/UIView+viewController.swift

@@ -7,7 +7,7 @@ extension UIView {
     /// The receiver’s view controller, or `nil` if it has none.
     ///
     /// This property is `nil` if the view has not yet been added to a view controller.
-    var viewController: UIViewController? {
+    public var _viewController: UIViewController? {
         if let nextResponder = self.next as? UIViewController {
             return nextResponder
         } else if let nextResponder = self.next as? UIView {

Sources/BetterSafariView/WebAuthenticationSession/WebAuthenticationPresentationModifier.swift → Sources/WebAuthenticationSession/WebAuthenticationPresentationModifier.swift

@@ -1,6 +1,7 @@
 #if os(iOS) || os(macOS) || os(watchOS)
 
 import SwiftUI
+import Shared
 
 struct WebAuthenticationPresentationModifier: ViewModifier {