Add this repository's git clone url to your container's app.yml file, at the bottom of the cmd section:
hooks:
after_code:
- exec:
cd: $home/plugins
cmd:
- mkdir -p plugins
- git clone https://github.com/discourse/docker_manager.git
- git clone https://github.com/JafethDC/discourse-chat-gitter.git
Rebuild your container:
cd /var/discourse
git pull
./launcher rebuild app