docs: update USERS.md (#3921)

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add kusionstack to Users

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USERS.md

@@ -31,6 +31,7 @@ Here's a running list of some organizations using GoReleaser[^1]:
 1. [IRON Security](https://iron.security)
 1. [Koordinator](https://koordinator.sh)
 1. [KSOC](https://www.ksoc.com/)
+1. [KusionStack](https://kusionstack.io/)
 1. [Mercure](https://mercure.rocks/)
 1. [Meroxa](https://meroxa.com/)
 1. [Microsoft](https://microsoft.com)