add a uniquie event for plugin function execution

Pilz.Plugins.Advanced/PluginFunction.cs

@@ -34,7 +34,14 @@ public abstract class PluginFunction : PluginFeature
 
     public virtual object? Execute(PluginFunctionParameter? @params)
     {
-        return ExecuteFunction(@params);
+        object? result = default;
+
+        if (!OnPreExecute(@params, ref result))
+            result = ExecuteFunction(@params);
+
+        OnPostExecute(@params, ref result);
+
+        return result;
     }
 
     protected abstract object? ExecuteFunction(PluginFunctionParameter? @params);