Add Dockerfile.

Dockerfile

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+FROM docker.io/library/debian:bullseye
+
+RUN apt update && \
+    apt upgrade -y && \
+    apt install -y curl && \
+    curl -o /etc/apt/sources.list.d/jpace121.list http://packages.jpace121.net/apt/jpace121.list && \
+    curl -o /etc/apt/trusted.gpg.d/jpace121.asc http://packages.jpace121.net/apt/jpace121.asc && \
+    apt update && \
+    apt install -y mosquitto j7s-mosquitto-plugin && \
+    rm -rf /var/lib/apt/lists/*
+
+ENTRYPOINT ["mosquitto"]