Add PURCHASE_NOTIFICATION message type (#2956)

Co-authored-by: Ivin <[email protected]>

Author: ivinjabraham

src/model/channel/message.rs

@@ -1032,6 +1032,7 @@ enum_number! {
         GuildIncidentAlertModeDisabled = 37,
         GuildIncidentReportRaid = 38,
         GuildIncidentReportFalseAlarm = 39,
+        PurchaseNotification = 44,
         _ => Unknown(u8),
     }
 }