Update 'ExtensionsEx.cs'

ExtensionsEx.cs

@@ -9,7 +9,23 @@
 // <copyright file="ExtensionsEx.cs" company="FCS">
 //     Copyright © FCS 2015-2022
 // </copyright>
-// <summary></summary>
+// <summary>
+//        Part of FCS.Lib - a set of utilities for C# - pieced together from fragments
+//        Copyright (C) 2021  FCS
+//
+//        This program is free software: you can redistribute it and/or modify
+//        it under the terms of the GNU Affero General Public License as
+//        published by the Free Software Foundation, either version 3 of the
+//        License, or (at your option) any later version.
+//
+//        This program is distributed in the hope that it will be useful,
+//        but WITHOUT ANY WARRANTY; without even the implied warranty of
+//        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//        GNU Affero General Public License for more details.
+//
+//        You should have received a copy of the GNU Affero General Public License
+//        along with this program.  If not, see <https://www.gnu.org/licenses/>.
+// </summary>
 // ***********************************************************************
 
 using System;