Add more boilerplate (#10)

example/Dockerfile

@@ -2,5 +2,11 @@
 ARG BUILD_FROM
 FROM $BUILD_FROM
 
+# Execute during the build of the image
+ARG TEMPIO_VERSION BUILD_ARCH
+RUN \
+    curl -sSLf -o /usr/bin/tempio \
+    "https://github.com/home-assistant/tempio/releases/download/${TEMPIO_VERSION}/tempio_${BUILD_ARCH}"
+
 # Copy data
-COPY rootfs /
+COPY rootfs /