[Feature] Per file attachement size limits (#3090)

* `SendFilesAsync` check file size per attachment instead of combined

* add `AttachmentSizeLimit` to interaction entites

src/Discord.Net.WebSocket/Entities/Interaction/SocketInteraction.cs

@@ -90,6 +90,9 @@ namespace Discord.WebSocket
         /// <inheritdoc cref="IDiscordInteraction.Entitlements" />
         public IReadOnlyCollection<RestEntitlement> Entitlements { get; private set; }
 
+        /// <inheritdoc/>
+        public ulong AttachmentSizeLimit { get; private set; }
+
         /// <inheritdoc/>
         public IReadOnlyDictionary<ApplicationIntegrationType, ulong> IntegrationOwners { get; private set; }
 
@@ -194,6 +197,8 @@ namespace Discord.WebSocket
                     _ => null
                 };
             }
+
+            AttachmentSizeLimit = model.AttachmentSizeLimit;
         }
 
         /// <summary>