fix: include MessageFlags and SuppressEmbedParams

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

@@ -0,0 +1,10 @@
+using System;
+
+namespace Discord.API
+{
+    [Flags]
+    internal enum MessageFlags : byte // probably safe to constrain this to 8 values, if not, it's internal so who cares
+    {
+        Suppressed = 0x04,
+    }
+}