As a user I would to be able to run a custom build script to build my app for the server

[thescientist13]

This would allow any user to build and bootstrap their app using their own npm script.

I think a good way to think about this is as a "hook", so in the Dockerfile it would be something like

# install your project's dependencies, run webpack, etc.  
# Output directory here should should match the first path of the next COPY command
RUN yarn ssr:hook:setup

And in the project's package.json

"scripts": {
  "build": "webpack --progress",
  "ssr:hook:setup": "npm install && npm run build",
}