Implement share/activity button on iOS

Multiplatform/iOS/Article/ArticleActivityItemSource.swift

@@ -0,0 +1,33 @@
+//
+//  ArticleActivityItemSource.swift
+//  Multiplatform iOS
+//
+//  Created by Maurice Parker on 7/13/20.
+//  Copyright © 2020 Ranchero Software. All rights reserved.
+//
+
+import UIKit
+
+class ArticleActivityItemSource: NSObject, UIActivityItemSource {
+	
+	private let url: URL
+	private let subject: String?
+	
+	init(url: URL, subject: String?) {
+		self.url = url
+		self.subject = subject
+	}
+	
+	func activityViewControllerPlaceholderItem(_ : UIActivityViewController) -> Any {
+		return url
+	}
+	
+	func activityViewController(_ activityViewController: UIActivityViewController, itemForActivityType activityType: UIActivity.ActivityType?) -> Any? {
+		return url
+	}
+	
+	func activityViewController(_ activityViewController: UIActivityViewController, subjectForActivityType activityType: UIActivity.ActivityType?) -> String {
+		return subject ?? ""
+	}
+	
+}