Added docker environment.

docker/Dockerfile

@@ -0,0 +1,25 @@
+FROM rust:1.57 as builder
+WORKDIR /usr/src/godaddy_ddns
+COPY . .
+RUN cargo install --path .
+
+FROM debian:buster-slim
+
+# Install dependencies.
+RUN apt-get update && \
+    apt-get install -y ca-certificates libssl-dev cron &&  \
+    rm -rf /var/lib/apt/lists/*
+
+# Add application from builder container.
+COPY --from=builder /usr/local/cargo/bin/godaddy_ddns /usr/local/bin/godaddy_ddns
+
+# Add crontab
+COPY --from=builder /usr/src/godaddy_ddns/docker/crontab /etc/cron.d/godaddy_ddns
+RUN chmod 0644 /etc/cron.d/godaddy_ddns
+RUN crontab /etc/cron.d/godaddy_ddns
+
+# Add entrypoint
+COPY --from=builder /usr/src/godaddy_ddns/docker/entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+CMD ["/entrypoint.sh"]