[Bug] Docker Hub README description gets truncated

See where it cuts off: https://hub.docker.com/r/freshrss/freshrss#option-3-cron-as-another-instance-of-the-same-freshrss-docker-image

It's a documented behavior: https://github.com/peter-evans/dockerhub-description#content-limits

It would be nice if we modified the README ourselves before passing it to dockerhub-description with a "Read more" link at the end, currently the description makes the README look incomplete.