Fix crosspost ratelimits (#2100)

src/Discord.Net.Rest/API/Common/Ratelimit.cs

@@ -0,0 +1,21 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord.API
+{
+    internal class Ratelimit
+    {
+        [JsonProperty("global")]
+        public bool Global { get; set; }
+
+        [JsonProperty("message")]
+        public string Message { get; set; }
+
+        [JsonProperty("retry_after")]
+        public double RetryAfter { get; set; }
+    }
+}