added test project for AdventOfCode.Extensions

AdventOfCode.Extensions/EnumerableExtensions.cs

@@ -18,7 +18,7 @@ public static class EnumerableExtensions
         {
             var validIndex = false;
             var currentIndex = 0;
-            foreach (var i in Range(0, count).Reverse())
+            for(var i = count - 1; i >= 0; i--)
             {
                 currentIndex = i;
                 if (indices[i] != i + poolLength - count)