feature: add Format.Url, Format.EscapeUrl

Format.Url formats a URL into a markdown `[]()` masked URL.

Format.EscapeUrl formats a URL into a Discord `<>` escaped URL.

src/Discord.Net.Core/Format.cs

@@ -14,6 +14,10 @@ namespace Discord
         public static string Underline(string text) => $"__{text}__";
         /// <summary> Returns a markdown-formatted string with strikethrough formatting. </summary>
         public static string Strikethrough(string text) => $"~~{text}~~";
+        /// <summary> Returns a markdown-formatted URL. Only works in <see cref="EmbedBuilder"/> descriptions and fields. </summary>
+        public static string Url(string text, string url) => $"[{text}]({url})";
+        /// <summary> Escapes a URL so that a preview is not generated. </summary>
+        public static string EscapeUrl(string url) => $"<{url}>";
 
         /// <summary> Returns a markdown-formatted string with codeblock formatting. </summary>
         public static string Code(string text, string language = null)