Add prod Dockerfile

[javierprovecho]

Add a prod Dockerfile for pilad with only 3 layers and weighting 11.2 MB. Also add DockerHub badge for /r/fern4lvarez/piladb in case of switching from dev image to prod image.

[fern4lvarez]

Hi @javierprovecho!

First of all, thanks for submitting the first external PR of the history of piladb! This is great! :tada:

I love the idea of having a super lightweight image for running pilad on Docker. So I'm in for that. But in the other hand I'm a bit skeptical about adding a Dockerfile to the project root, as I'm obsess with keeping it clean, having on it only files related to the project itself, and not with the code, deployment or operational issues.

I'm thinking on these options in order to find a good compromise:

• Integrating it into the dev directory, and documenting differences between the dev and the prod Dockerfiles and their usage.
• Create a new directory dedicated production releases, e.g. prod, deploy, etc., where we can store this new Dockerfile and document how to use it. We can also document in this directory another deployment good practices, etc.

These are just ideas, you don't need to do it all now, just discuss an approach where we both agree and work on that.

For what it's worth, I will not merge this for now until we find the right way. :relieved:

[javierprovecho]

@fern4lvarez sure!, I suggest creating a /prod or /deploy directory with its own README and maybe some examples in K8S and/or Compose. Do you agree?

[fern4lvarez]

@javierprovecho Let's go for deploy directory. All things containers (Dockerfile, k8s's chart, etc.) can live here.

Do you want to work on it? If so, please fix the conflicts, moving the new DockerHub badge to the dev's README file.