Switch to current-alpine to slim down Docker builds

[kprinssu]

This PR will change the base Docker images to use the latest Node version on top of the slimmed down Alpine images.

[Inrixia]

Why was this closed?

[kprinssu]

Apologies, I was making sure the container was functional and it is 🎉 !

[Inrixia]

What's the size difference of the image after these changes?

[kprinssu]

It's about 2/3 size of the normal images:

# docker image ls | grep floatplane
kprinssu/floatplane-downloader        dev             789116f7076c   27 hours ago        237MB
inrix/floatplane-downloader           dev             90340801283b   5 days ago          301MB

The base alpine images remove a lot of cruft.

[Inrixia]

Awesome thanks!