Add Sanitize function to escape Markdown (#249)

src/Discord.Net/Format.cs

@@ -2,6 +2,9 @@
 {
     public static class Format
     {
+        // Characters which need escaping
+        private static string[] SensitiveCharacters = { "*", "_", "~", "`", "\\" };
+
         /// <summary> Returns a markdown-formatted string with bold formatting. </summary>
         public static string Bold(string text) => $"**{text}**";
         /// <summary> Returns a markdown-formatted string with italics formatting. </summary>
@@ -19,5 +22,15 @@
             else
                 return $"`{text}`";
         }
+
+        /// <summary> Sanitizes the string, safely escaping any Markdown sequences. </summary>
+        public static string Sanitize(string text)
+        {
+            foreach (string unsafeChar in SensitiveCharacters)
+            {
+                text = text.Replace(unsafeChar, $"\\{unsafeChar}");
+            }
+            return text;
+        }
     }
 }