Expand Plugin and REST APIs to trigger user typing event (#14331)

app/app_iface.go

@@ -774,6 +774,7 @@ type AppIface interface {
 	ProcessSlackText(text string) string
 	Publish(message *model.WebSocketEvent)
 	PublishSkipClusterSend(message *model.WebSocketEvent)
+	PublishUserTyping(userId, channelId, parentId string) *model.AppError
 	PurgeBleveIndexes() *model.AppError
 	PurgeElasticsearchIndexes() *model.AppError
 	ReadFile(path string) ([]byte, *model.AppError)