add extension_list example (#281)

- Created an example of extension policy
- Added C# binding support of .NET framework 4.0 and created a Nuget
  spec for it.
- Added a pytest in python bindings to test the extension policy and the
  python binding
- Restructured the example and Csharp binding directories due to above
  changes.
- Added copyrights.
- Added a Windows workflow for .NET 4.0 build and test.

bindings/csharp/net8.0/Program.cs

@@ -0,0 +1,68 @@
+//-----------------------------------------------------------------------
+// <copyright file="Program.cs" company="Microsoft">
+//    Copyright (c)2012 Microsoft. All rights reserved.
+// </copyright>
+// <summary>
+//    Contains code to test the Regorus class for C#
+// and .NET 8.0 bindings. 
+// </summary>
+//-----------------------------------------------------------------------
+
+using System.Diagnostics;
+
+long nanosecPerTick = (1000L*1000L*1000L) / Stopwatch.Frequency;
+var w = new Stopwatch();
+
+
+// Force load of modules.
+{
+    var _e = new Regorus.Engine();
+    var _j = System.Text.Json.JsonDocument.Parse("{}");
+}
+
+w.Restart();
+
+var engine = new Regorus.Engine();
+
+w.Stop();
+var newEngineTicks = w.ElapsedTicks;
+
+
+w.Restart();
+
+// Load policies and data.
+engine.AddPolicyFromFile("../../../tests/aci/framework.rego");
+engine.AddPolicyFromFile("../../../tests/aci/api.rego");
+engine.AddPolicyFromFile("../../../tests/aci/policy.rego");
+engine.AddDataFromJsonFile("../../../tests/aci/data.json");
+
+
+w.Stop();
+var loadPoliciesTicks = w.ElapsedTicks;
+
+
+w.Restart();
+
+// Set input and eval rule.
+engine.SetInputFromJsonFile("../../../tests/aci/input.json");
+var value = engine.EvalQuery("data.framework.mount_overlay");
+var valueDoc = System.Text.Json.JsonDocument.Parse(value);
+
+w.Stop();
+var evalTicks = w.ElapsedTicks;
+
+Console.WriteLine("{0}", valueDoc);
+
+
+Console.WriteLine("Engine creation took {0} msecs", (newEngineTicks*nanosecPerTick)/(1000.0*1000.0));
+Console.WriteLine("Load policies and data took {0} msecs", (loadPoliciesTicks*nanosecPerTick)/(1000.0*1000.0));
+Console.WriteLine("EvalQuery took {0} msecs", (evalTicks*nanosecPerTick)/(1000.0*1000.0));
+
+engine = new Regorus.Engine();
+engine.AddPolicy(
+  "test.rego", 
+  "package test\nx = 1\nmessage = `Hello`");
+
+engine.SetEnableCoverage(true);
+Console.WriteLine("{0}", engine.EvalRule("data.test.message"));
+Console.WriteLine("{0}", engine.GetCoverageReportPretty());