Add scoped searching of articles

Shared/SmartFeeds/SearchTimelineFeedDelegate.swift

@@ -0,0 +1,31 @@
+//
+//  SearchTimelineFeedDelegate.swift
+//  NetNewsWire
+//
+//  Created by Maurice Parker on 8/31/19.
+//  Copyright © 2019 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+import Account
+import Articles
+
+struct SearchTimelineFeedDelegate: SmartFeedDelegate {
+
+	var nameForDisplay: String {
+		return nameForDisplayPrefix + searchString
+	}
+
+	let nameForDisplayPrefix = NSLocalizedString("Search: ", comment: "Search smart feed title prefix")
+	let searchString: String
+	let fetchType: FetchType
+
+	init(searchString: String, articleIDs: Set<String>) {
+		self.searchString = searchString
+		self.fetchType = .searchWithArticleIDs(searchString, articleIDs)
+	}
+
+	func fetchUnreadCount(for: Account, callback: @escaping (Int) -> Void) {
+		// TODO: after 5.0
+	}
+}