Fix #4025: add user setting to keep the view mode.

Oqtane.Shared/Enums/ViewMode.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Oqtane.Enums
+{
+    public enum ViewMode
+    {
+        View,
+        Edit
+    }
+}