Add doc comment about notification flags

src/module.c

@@ -3716,6 +3716,7 @@ void moduleReleaseGIL(void) {
  *  - REDISMODULE_NOTIFY_ZSET: Sorted Set events
  *  - REDISMODULE_NOTIFY_EXPIRED: Expiration events
  *  - REDISMODULE_NOTIFY_EVICTED: Eviction events
+ *  - REDISMODULE_NOTIFY_STREAM: Stream events
  *  - REDISMODULE_NOTIFY_ALL: All events
  * 
  * We do not distinguish between key events and keyspace events, and it is up