Add time zones settings panel

Data.cs

@@ -0,0 +1,21 @@
+using System.Collections.ObjectModel;
+using System.Text.Json;
+using WorldClockStatusWindow.Properties;
+
+namespace WorldClockStatusWindow;
+
+internal static class Data
+{
+    internal static ObservableCollection<TimeZoneEntry> TimeZoneEntries { get; set; }
+
+    internal static void Load()
+    {
+        TimeZoneEntries = JsonSerializer.Deserialize<ObservableCollection<TimeZoneEntry>>(Settings.Default.TimeZones);
+    }
+
+    internal static void Save()
+    {
+        Settings.Default.TimeZones = JsonSerializer.Serialize(TimeZoneEntries);
+        Settings.Default.Save();
+    }
+}