Fix node version at 12 (#149)

#136 (comment)

Author: RobbertH

{{cookiecutter.project_slug}}/frontend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:latest
+FROM node:12
 
 ADD package.json /package.json
 
@@ -13,4 +13,4 @@ EXPOSE 8000
 EXPOSE 35729
 
 ENTRYPOINT ["/bin/bash", "/app/run.sh"]
-CMD ["start"]
+CMD ["start"]