Add csharp thread pool example

[warrenkeil]

Proposed changes:

Adding an example of thread pooling using c#.

Tests:

I ran the example locally using .Net 6, to ensure it is working.

To run this file:

1. Add a new console application using .Net 6. You can do this easily with Rider or Visual Studio
2. Paste the following over the contents of the Program.cs file:

   
   using ThreadTest;

Console.WriteLine("Hello, starting thread pool example!"); ThreadPoolExample.DoMultiThreadedWork(); Console.WriteLine("--> Finished!");