Add cache:warmup deployment step (#361)

bin/docker-entrypoint

@@ -9,6 +9,8 @@ fi
 # If running the rails server then create or migrate existing database
 if [ "${@: -2:1}" == "./bin/rails" ] && [ "${@: -1:1}" == "server" ]; then
   ./bin/rails db:prepare
+  echo "Warming up caches for production deployment..."
+  ./bin/rails cache:warmup
 fi
 
 exec "${@}"