[MINOR] docs: Update MAINTAINERS.md (#3452)

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### What changes were proposed in this pull request?

Add PoAn Yang (FrankYang0529) to Contributors list.

Signed-off-by: PoAn Yang <payang@apache.org>

MAINTAINERS.md

@@ -41,6 +41,7 @@ Contributors may be added by existing maintainers (see [Governance document](GOV
 | Han Zhang      | xiaozcy             | Xiaomi           |
 | Yu-Hsin Lai    | laiyousin           | Virginia Tech    |
 | Charlie Cheng  | charliecheng630     | cacaFly          |
+| PoAn Yang      | FrankYang0592       | SUSE             |
 
 
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