Patch; Regex doesnt respect case-sensitive url's

src/Discord.Net.Webhook/DiscordWebhookClient.cs

@@ -33,7 +33,7 @@ namespace Discord.Webhook
             : this(webhookUrl, new DiscordRestConfig()) { }
 
         // regex pattern to match webhook urls
-        private static Regex WebhookUrlRegex = new Regex(@"^.*(discord|discordapp)\.com\/api\/webhooks\/([\d]+)\/([a-z0-9_-]+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);
+        private static Regex WebhookUrlRegex = new Regex(@"^.*(discord|discordapp)\.com\/api\/webhooks\/([\d]+)\/([a-zA-Z0-9_-]+)$", RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);
 
         /// <summary> Creates a new Webhook Discord client. </summary>
         public DiscordWebhookClient(ulong webhookId, string webhookToken, DiscordRestConfig config)