Documentation needed for new tags

[ibennetch]

It would be great to update the documentation in https://github.com/phpmyadmin/docker/blob/master/README.md and https://github.com/phpmyadmin/phpmyadmin/blob/master/doc/setup.rst#installing-using-docker with information about working with the new tags from #200.

[J0WI]

Some is done in #216