some improvements

Pilz.UI/Highlighter.cs

@@ -442,7 +442,7 @@ public class Highlighter : Component
         }
     }
 
-    private Timer _DelayTimer = null;
+    private System.Windows.Forms.Timer _DelayTimer = null;
 
     private void ContainerControlSizeChanged(object sender, EventArgs e)
     {
@@ -453,7 +453,7 @@ public class Highlighter : Component
 
             if (_DelayTimer is null)
             {
-                _DelayTimer = new Timer();
+                _DelayTimer = new();
                 _DelayTimer.Interval = 100;
                 _DelayTimer.Tick += new EventHandler(DelayTimerTick);
                 _DelayTimer.Start();