Add Rot13 in Beef (#3732)

archive/b/beef/Rot13.bf

@@ -0,0 +1,45 @@
+using System;
+
+namespace Rot13;
+
+class Program
+{
+    public static void Usage()
+    {
+        Console.WriteLine("Usage: please provide a string to encrypt");
+        Environment.Exit(0);
+    }
+
+    public static void Rot13(StringView str, ref String result)
+    {
+        result.Clear();
+        result.Reserve(str.Length);
+        for (char8 ch in str)
+        {
+            char8 chLower = ch.ToLower;
+            if (chLower >= 'a' && chLower <= 'm')
+            {
+                ch += 13;
+            }
+            else if (chLower >= 'n' && chLower <= 'z')
+            {
+                ch -= 13;
+            }
+
+            result += ch;
+        }
+    }
+
+    public static int Main(String[] args)
+    {
+        if (args.Count < 1 || args[0].Length < 1)
+        {
+            Usage();
+        }
+
+        String result = scope String();
+        Rot13(args[0], ref result);
+        Console.WriteLine(result);
+        return 0;
+    }
+}