Added Npgsql licence information (#25)

Author: droyad

src/dbup-postgresql/Npgsql-LICENSE

@@ -0,0 +1,17 @@
+Copyright (c) 2002-2021, Npgsql
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose, without fee, and without a written agreement
+is hereby granted, provided that the above copyright notice and this
+paragraph and the following two paragraphs appear in all copies.
+
+IN NO EVENT SHALL NPGSQL BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
+SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS,
+ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
+Npgsql HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+NPGSQL SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED
+TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND Npgsql
+HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS,
+OR MODIFICATIONS.

src/dbup-postgresql/PostgresqlQueryParser.cs

@@ -1,4 +1,8 @@
-#nullable enable
+// This code based on original code from Npgsql
+// https://github.com/npgsql/npgsql/blob/main/src/Npgsql/SqlQueryParser.cs
+// which is BSD license: https://github.com/npgsql/npgsql/blob/main/LICENSE
+
+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;