Prepare for selection of items

Update MainView.swift

CHDataManagement/Main/SelectedContent.swift

@@ -0,0 +1,22 @@
+import Foundation
+
+final class SelectedContent: ObservableObject {
+
+    @Published
+    var tab: MainViewTab = .posts
+
+    @Published
+    var post: Post?
+
+    @Published
+    var page: Page?
+
+    @Published
+    var tag: Tag?
+
+    @Published
+    var file: FileResource?
+
+    @Published
+    var section: SettingsSection = .folders
+}