Set USER node in Dockerfile

root user prevents prepublish scripts from running in npm.

Dockerfile

@@ -16,5 +16,7 @@ RUN chmod 700 ~/.ssh
 RUN touch ~/.ssh/known_hosts
 RUN chmod 644 ~/.ssh/known_hosts
 
+USER node
+
 COPY src/ build/
 CMD ["/build/release.sh"]
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