feat: GuildForum supports webhook (#1720)

Signed-off-by: retr0-init <146389702+retr0-init@users.noreply.github.com>

Author: retr0-init

interactions/models/discord/channel.py

@@ -2399,7 +2399,7 @@ async def close_stage(self, reason: Absent[Optional[str]] = MISSING) -> None:
 
 
 @attrs.define(eq=False, order=False, hash=False, kw_only=True)
-class GuildForum(GuildChannel, InvitableMixin):
+class GuildForum(GuildChannel, InvitableMixin, WebhookMixin):
     available_tags: List[ThreadTag] = attrs.field(repr=False, factory=list)
     """A list of tags available to assign to threads"""
     default_reaction_emoji: Optional[DefaultReaction] = attrs.field(repr=False, default=None)