feat(languages): add C# support

templates/solution/cs/Solution.cs

@@ -0,0 +1,15 @@
+namespace Solution
+{
+  class Program
+  {
+    static void Main()
+    {
+      string line;
+      while ((line = System.Console.ReadLine()) != null)
+      {
+
+        System.Console.WriteLine($"Hello, {line}!");
+      }
+    }
+  }
+}