docs: add elastic as alt log backend

看了一下，openobverse似乎更像是promethus/grafana一样的系统监控日志而非是纯日志。它和netdata作伴去吧。

elastic起码还是有一些logging可用的handler的

https://pypi.org/project/elasticsearch-logging-handler/

src/yuheng/basic/log.py

@@ -1,4 +1,5 @@
 import os
+
 # import logging.config
 
 from loguru import logger as loguru_logger
@@ -50,8 +51,8 @@
 # logger.add(sink=logging_handler_sls, format=loguru_format, **loguru_config)
 # clickhouse
 # logger.add(sink=logging_handler_clickhouse)
-# openobserve
-# logger.add(sink=logging_handler_openobserve)
+# elasticsearch
+# logger.add(sink=logging_handler_elasticsearch)
 
 # logger.disable("yuheng")
 logger.info("loguru enabled")