Return POST_EMBED_LINK for links that are not images nor og (#11723)

model/post_embed.go

@@ -7,6 +7,7 @@ const (
 	POST_EMBED_IMAGE              PostEmbedType = "image"
 	POST_EMBED_MESSAGE_ATTACHMENT PostEmbedType = "message_attachment"
 	POST_EMBED_OPENGRAPH          PostEmbedType = "opengraph"
+	POST_EMBED_LINK               PostEmbedType = "link"
 )
 
 type PostEmbedType string