fix: add tini as PID 1 to prevent zombie processes in containers

universal-runtime/Dockerfile

@@ -3,6 +3,7 @@ FROM debian:bookworm-slim
 ENV DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
+    tini \
     chromium \
     xvfb \
     x11vnc \
@@ -23,4 +24,4 @@ COPY manager.py /manager.py
 RUN chmod +x /entrypoint.sh
 
 EXPOSE 6080
-ENTRYPOINT ["/entrypoint.sh"]
+ENTRYPOINT ["/usr/bin/tini", "--", "/entrypoint.sh"]