Make docker-compose build static to a external folder

[adfslslddkds]

Some fix for https://github.com/umputun/remark42/issues/1178 it looks lite Dockerfile and docker-compose.yml can't generate static to a folder. Site source generated in Dockerfile stored in /srv/ folder looks like for some production reasons. And this container can't be used for development.

I add my version how it should work for development actually it is only a draft.

[umputun]

Site source generated in Dockerfile stored in /srv/ folder looks like for some production reasons. And this container can't be used for development.

This container can be started at any moment in any dockerized environment with docker run -p 8080:8080 ghcr.io/umputun/remark24-site:master and accessed locally http://localhost:8080/docs/getting-started/installation/