Refactoring c# projects (#544)

Small Refactoring c# projects, e.g.
* add days
* remove StartupObject
* Fix Approval tests for NUnit
* Use Environment.NewLine in Xunit tests
* Added + fixed README.md
* Removed global.json

csharp.xUnit/GildedRoseTests/GildedRoseTest.cs

@@ -2,17 +2,16 @@
 using System.Collections.Generic;
 using GildedRoseKata;
 
-namespace GildedRoseTests
+namespace GildedRoseTests;
+
+public class GildedRoseTest
 {
-    public class GildedRoseTest
+    [Fact]
+    public void foo()
     {
-        [Fact]
-        public void foo()
-        {
-            IList<Item> Items = new List<Item> { new Item { Name = "foo", SellIn = 0, Quality = 0 } };
-            GildedRose app = new GildedRose(Items);
-            app.UpdateQuality();
-            Assert.Equal("fixme", Items[0].Name);
-        }
+        IList<Item> Items = new List<Item> { new Item { Name = "foo", SellIn = 0, Quality = 0 } };
+        GildedRose app = new GildedRose(Items);
+        app.UpdateQuality();
+        Assert.Equal("fixme", Items[0].Name);
     }
-}
+}