Use ruby alpine as base image

[karunsiri]

I believe the dependencies added are the least required by Rails and Puma.

• build-base for compiling gems using native extensions
• git is required when running rails new
• libressl-dev is required by Puma, in case you bind SSL certificates directly
• libxml2-dev is for XML parser. Like nokogiri.
• tzdata Timezone

The new Dockerfile will reduce the final image to about 550MB, uncompressed.

Changes

• Adds build arguments: RUBY_VERSION (defaults: 3.1) and NODE_VERSION (defaults: 19)
• Use ruby alpine as base image.
• Use multistage build to pull in binaries from node without having to reinstall node.

Contributes to #10

[karunsiri]

Please consider the fact that most of the time, for alpine images, you will have a harder time figuring out the needed libraries required to build native extension gems. It comes super light weight, but needs super explicit tooling/libraries.

[dhh]

Yeah I don't think it's worth switching to alpine for this reason. Whole point is for this image to make it super easy for beginners. They can't go debugging dependency issues. Appreciate the attempt, though ✌️❤️.