If you're after easy hosting of dockerized web services with automatic certificate enrolment using Lets Encrypt, then the solution is to use 2 docker containers - nginx as a web proxy and Lets Encrypt Companion to handle certificates. LE Companion can provide either LIVE or STAGING certificates, depending on configuration, but you can run only one at a time.
Container definitions below are in a docker-compose format and the recipe below contains absolutely no security hardening of the Docker installation - this is something you need to consider separately
TLSproxy is nginx based reverse proxy that automatically discovers and configures virtual hosts running on the same machine. See image description on docker hub for details. TL;DR simple approach is:
docker run -d -e VIRTUAL_HOST=blog.domain.tld ghost
Please note, the DEFAULT_HOST variable - it's quite useful to have it set right :-)