Add container runtime

Containerfile

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+FROM docker.io/library/ruby:3.3
+
+ARG SMASHING_VERSION
+
+RUN gem install smashing -v ${SMASHING_VERSION}
+RUN apt update --yes
+RUN apt install nodejs --yes
+RUN apt clean all
+RUN mkdir --parents /smashing
+
+ENV SMASHING_PROJECT_DIR=/smashing
+
+ADD container-entrypoint.sh /container-entrypoint.sh
+
+ENTRYPOINT ["/container-entrypoint.sh"]
+
+CMD ["start"]