Adding new maintainer @yuancu (#4045)

* Adding new maintainer @yuancu

Signed-off-by: Lantao Jin <ltjin@amazon.com>

* Update CODEOWNERS

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Update CODEOWNERS

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Update MAINTAINERS.md

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

---------

Signed-off-by: Lantao Jin <ltjin@amazon.com>
Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>
Co-authored-by: Peter Zhu <zhujiaxi@amazon.com>

Author: LantaoJin

.github/CODEOWNERS

@@ -1,2 +1,2 @@
 # This should match the owning team set up in https://github.com/orgs/opensearch-project/teams
-*   @pjfitzgibbons @ps48 @kavithacm @derek-ho @joshuali925 @dai-chen @YANG-DB @rupal-bq @mengweieric @vamsi-amazon @swiddis @penghuo @seankao-az @MaxKsyunz @Yury-Fridlyand @anirudha @forestmvey @acarbonetto @GumpacG @ykmr1224 @LantaoJin @noCharger @qianheng-aws
+*   @ps48 @kavithacm @derek-ho @joshuali925 @dai-chen @YANG-DB @mengweieric @vamsimanohar @swiddis @penghuo @seankao-az @MaxKsyunz @Yury-Fridlyand @anirudha @forestmvey @acarbonetto @GumpacG @ykmr1224 @LantaoJin @noCharger @qianheng-aws @yuancu

MAINTAINERS.md

@@ -10,10 +10,8 @@ This document contains a list of maintainers in this repo. See [opensearch-proje
 | Joshua Li         | [joshuali925](https://github.com/joshuali925)       | Amazon      |
 | Shenoy Pratik     | [ps48](https://github.com/ps48)                     | Amazon      |
 | Kavitha Mohan     | [kavithacm](https://github.com/kavithacm)           | Amazon      |
-| Rupal Mahajan     | [rupal-bq](https://github.com/rupal-bq)             | Amazon      |
 | Derek Ho          | [derek-ho](https://github.com/derek-ho)             | Amazon      |
 | Lior Perry        | [YANG-DB](https://github.com/YANG-DB)               | Amazon      |
-| Peter Fitzgibbons | [pjfitzgibbons](https://github.com/pjfitzgibbons)   | Amazon      |
 | Simeon Widdis     | [swiddis](https://github.com/swiddis)               | Amazon      |
 | Chen Dai          | [dai-chen](https://github.com/dai-chen)             | Amazon      |
 | Vamsi Manohar     | [vamsimanohar](https://github.com/vamsimanohar)     | Amazon      |
@@ -24,6 +22,7 @@ This document contains a list of maintainers in this repo. See [opensearch-proje
 | Lantao Jin        | [LantaoJin](https://github.com/LantaoJin)           | Amazon      |
 | Louis Chu         | [noCharger](https://github.com/noCharger)           | Amazon      |
 | Heng Qian         | [qianheng-aws](https://github.com/qianheng-aws)     | Amazon      |
+| Yuanchun Shen     | [yuancu](https://github.com/yuancu)                 | Amazon      |
 | Max Ksyunz        | [MaxKsyunz](https://github.com/MaxKsyunz)           | Improving   |
 | Yury Fridlyand    | [Yury-Fridlyand](https://github.com/Yury-Fridlyand) | Improving   |
 | Andrew Carbonetto | [acarbonetto](https://github.com/acarbonetto)       | Improving   |
@@ -40,3 +39,6 @@ This document contains a list of maintainers in this repo. See [opensearch-proje
 | Eugene Lee        | [eugenesk24](https://github.com/eugenesk24)             | Amazon      |
 | Zhongnan Su       | [zhongnansu](https://github.com/zhongnansu)             | Amazon      |
 | Chloe Zhang       | [chloe-zh](https://github.com/chloe-zh)                 | Amazon      |
+| Peter Fitzgibbons | [pjfitzgibbons](https://github.com/pjfitzgibbons)       | Amazon      |
+| Rupal Mahajan     | [rupal-bq](https://github.com/rupal-bq)                 | Amazon      |
+