feat: respect guild boost file size limit when re-sending attachments

Myriad/Extensions/GuildExtensions.cs

@@ -1,7 +1,22 @@
+using Myriad.Types;
+
 namespace Myriad.Extensions
 {
     public static class GuildExtensions
     {
-
+        public static int FileSizeLimit(this Guild guild)
+        {
+            switch (guild.PremiumTier)
+            {
+                default:
+                case PremiumTier.NONE:
+                case PremiumTier.TIER_1:
+                    return 8;
+                case PremiumTier.TIER_2:
+                    return 50;
+                case PremiumTier.TIER_3:
+                    return 100;
+            }
+        }
     }
 }