add maintainer

Signed-off-by: zhichao-aws <[email protected]>

MAINTAINERS.md

@@ -23,5 +23,6 @@
 | Subhobrata DEY        | [sbcd90](https://github.com/sbcd90)                 | Amazon      |
 | Zhichao Geng          | [zhichao-aws](https://github.com/zhichao-aws)       | Amazon      |
 | Joshua Li             | [joshuali925](https://github.com/joshuali925)       | Amazon      |
+| Hailong Cui             | [hailong-am](https://github.com/hailong-am)       | Amazon      |
 
 [This document](https://github.com/opensearch-project/.github/blob/main/MAINTAINERS.md) explains what maintainers do in this repo, and how they should be doing it. If you're interested in contributing, see [CONTRIBUTING](CONTRIBUTING.md).