Add message flag for forwarded messages (#7253)

Author: Qreepex

docs/resources/Message.md

@@ -143,6 +143,7 @@ Represents a message sent in a channel within Discord.
 | FAILED_TO_MENTION_SOME_ROLES_IN_THREAD | `1 << 8`  | this message failed to mention some roles and add their members to the thread     |
 | SUPPRESS_NOTIFICATIONS                 | `1 << 12` | this message will not trigger push and desktop notifications                      |
 | IS_VOICE_MESSAGE                       | `1 << 13` | this message is a voice message                                                   |
+| HAS_SNAPSHOT                           | `1 << 14` | this message has a snapshot (via Message Forwarding)                              |
 
 ###### Example Message