Alternative Docker images based on Ubuntu and Alpine

[lolgab]

It would be nice to have alternative official docker images that run on Ubuntu and Alpine, which are two of the most used base images.

[thresheek]

Hi @lolgab!

I'm not sure Ubuntu-ones are warranted since Debian-based ones are ubiquitous in Docker official images.

Regarding Alpine, this is worth exploring. Maybe language variants will be smaller than what's provided by current Debian-based images.

[thresheek]

See also https://github.com/nginx/unit/issues/777