add NavBarUtils class

deltachat-ios/Helper/Utils.swift

@@ -155,6 +155,19 @@ struct Utils {
     }
 }
 
+class NavBarUtils {
+    static func setBigTitle(navigationController: UINavigationController?) {
+        if #available(iOS 11.0, *) {
+            navigationController?.navigationBar.prefersLargeTitles = true
+        }
+    }
+    static func setSmallTitle(navigationController: UINavigationController?) {
+        if #available(iOS 11.0, *) {
+            navigationController?.navigationBar.prefersLargeTitles = false
+        }
+    }
+}
+
 class DateUtils {
     // TODO: refactor that, it's an improper way for localizations, use stringsdict instead
     // blocked by: converting androids plurals xml entries to stringsdict