Add ShouJian Zheng (@jianzs) as vLLM Ascend maintainer (#1203)

### What this PR does / why we need it?

Add @jianzs as vLLM Ascend maintainer

@jianzs
----
I would like to nominate Shoujian Zheng (@jianzs
<https://github.com/jianzs>) as a maintainer, starting with my +1.

- He focuses on the code quality and good design with solid reviews in P/D
disaggregation and DeepSeek improvement area about 30+ high quality review, such
as #issuecomment-2811764833, #discussion_r2069927605 and
#pullrequestreview-2820996674. This is the most important reason why I nominated
him, because helping community developers complete PRs with high quality and
continuously ensure the quality of codebase is one of the important
responsibilities of a maintainer. We believe he is a great addition.
- Shoujian's main expertise is distributed inference. He has a lot of experience
in production about AI infra. He has very good habits and explains in great
detail all changes #issue-3023082580 anqd share results open:
#issuecomment-2853140443. And High quality PR: #706, #774, #852.
- Community Involvement: Active involved in community discussion, he is
collaborative and helps the users solve problems, involved in 30+ PR and issue,
such as #issuecomment-2911934292 and #issuecomment-2833523571.

Reference:
[1] https://vllm-ascend.readthedocs.io/en/latest/community/contributors.html
[2] https://vllm-ascend.readthedocs.io/en/latest/community/governance.html

Signed-off-by: Yikun Jiang <yikunkero@gmail.com>

Author: Yikun

docs/source/community/contributors.md

@@ -7,6 +7,7 @@
 | Xiyuan Wang| [@wangxiyuan](https://github.com/wangxiyuan) | 2025/01 |
 | Yikun Jiang| [@Yikun](https://github.com/Yikun) | 2025/02 |
 | Yi Gan| [@ganyi1996ppo](https://github.com/ganyi1996ppo) | 2025/02 |
+| Shoujian Zheng| [@jianzs](https://github.com/jianzs) | 2025/06 |
 
 ## Contributors