Quick Messages Plugin

I opened

nano app.yml

opened this file and add this code

hooks:
  after_code:
    - exec:
        cd: $home/plugins
        cmd:
          - mkdir -p plugins
          - git clone https://github.com/angusmcleod/discourse-quick-messages.git

after saved file, I rebuild docker via

cd /var/discourse
./launcher rebuild app

But I can’t see this plugin in plugin area, and in my messenger. Why?