new FormRestRequest used for sending form data in url encoded format.

src/Discord.Net.Rest/Net/Queue/Requests/FormRestRequest.cs

@@ -0,0 +1,22 @@
+using Discord.Net.Rest;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Discord.Net.Queue
+{
+    public class FormRestRequest : RestRequest
+    {
+        public IEnumerable<KeyValuePair<string?, string?>> FormData { get; }
+
+        public FormRestRequest(IRestClient client, string method, string endpoint, IEnumerable<KeyValuePair<string?, string?>> formData, RequestOptions options)
+            : base(client, method, endpoint, options)
+        {
+            FormData = formData;
+        }
+
+        public override async Task<RestResponse> SendAsync()
+        {
+            return await Client.SendAsync(Method, Endpoint, FormData, Options.CancelToken, Options.HeaderOnly, Options.AuditLogReason).ConfigureAwait(false);
+        }
+    }
+}