Document usage with govuk-docker
Document usage with govuk-docker

Following precedent set in https://github.com/alphagov/content-publisher/pull/2257,
we have a Technical Documentation section describing the nature
of the app and how we can use GOV.UK Docker to run it. I've removed
the outdated reference to startup.sh.

I've also moved the previous technical preamble to a Further
Documentation section, as we've done elsewhere, keeping the
Technical Documentation section short and readable. This is an
intermediary step and I will extract this content out into separate
docs/ later.

alphagov/content-store,alphagov/content-store