Consider moving to multi-stage build instead of a single-stage script

[Qix-]

Iterative changes to this image are pretty painful I'd imagine 🙃

Now that Docker has multi-stage builds, it'd be pretty trivial to break out the single RUN into multiple layers, with an ultimate FROM alpine again in order to COPY --from all of the artifacts from the source build.

This would allow for proper Docker-ized layers whilst keeping the image size down since all of the intermediate layers of the original build step are omitted from the eventual docker push.

Might be worth considering :)

[OmgImAlexis]

The README has multi-stage builds https://github.com/mhart/alpine-node#example-dockerfile-for-your-own-nodejs-project