added arm64 support for multi user nix in docker (#1605)

## Summary
title says it 

## How was it tested?
not tested, 
CICD will break if issues arise.

Author: mohsenari

.github/workflows/docker-image-release.yml

@@ -31,4 +31,5 @@ jobs:
           context: ./internal/impl/generate/tmpl/
           file: ./internal/impl/generate/tmpl/DevboxImageDockerfileRootUser
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: jetpackio/devbox-root-user:latest