Add 'govuk-docker' to list of GOV.UK applications
Add 'govuk-docker' to list of GOV.UK applications

It could be considered a utility, like 'govuk-dependencies'.
Including this repo pulls in its README and `docs/` folder, which
should be useful for developers.

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs