You can’t. You’ll need to create a custom image that has a little more stuff in it than the base image includes. For some hints on what you’ll need to do, see Can Discourse ship frequent Docker images that do not need to be bootstrapped? for starters.
I’m working on the same problem and hope to have a solution (that solves my specific set of problems) in the next month. I won’t share it here because it’ll be a support nightmare that meta is not designed to handle. At some point I will consider making those images available, but only when I’m sure that meta won’t be flooded with support requests.