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.NUnit/GildedRose/Program.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+
+namespace GildedRoseKata;
+
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        Console.WriteLine("OMGHAI!");
+
+        IList<Item> items = new List<Item>
+        {
+            new Item {Name = "+5 Dexterity Vest", SellIn = 10, Quality = 20},
+            new Item {Name = "Aged Brie", SellIn = 2, Quality = 0},
+            new Item {Name = "Elixir of the Mongoose", SellIn = 5, Quality = 7},
+            new Item {Name = "Sulfuras, Hand of Ragnaros", SellIn = 0, Quality = 80},
+            new Item {Name = "Sulfuras, Hand of Ragnaros", SellIn = -1, Quality = 80},
+            new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                SellIn = 15,
+                Quality = 20
+            },
+            new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                SellIn = 10,
+                Quality = 49
+            },
+            new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                SellIn = 5,
+                Quality = 49
+            },
+            // this conjured item does not work properly yet
+            new Item {Name = "Conjured Mana Cake", SellIn = 3, Quality = 6}
+        };
+
+        var app = new GildedRose(items);
+
+        int days = 2;
+        if (args.Length > 0)
+        {
+            days = int.Parse(args[0]) + 1;
+        }
+
+        for (var i = 0; i < days; i++)
+        {
+            Console.WriteLine("-------- day " + i + " --------");
+            Console.WriteLine("name, sellIn, quality");
+            for (var j = 0; j < items.Count; j++)
+            {
+                Console.WriteLine(items[j].Name + ", " + items[j].SellIn + ", " + items[j].Quality);
+            }
+            Console.WriteLine("");
+            app.UpdateQuality();
+        }
+    }
+}