Persist certificates between container restarts

[ali-ramadhan]

To avoid hitting https://letsencrypt.org/docs/rate-limits/ with v2.0.0+ of https://github.com/nginx-proxy/docker-letsencrypt-nginx-proxy-companion we need to persist certificates. From their README:

The single most important change is that the container now requires a volume mounted to /etc/acme.sh in order to persist ACME account keys and SSL certificates.

X-Ref: testdrivenio/django-on-docker-letsencrypt#9

[ali-ramadhan]

Actually looks easy from these examples: https://github.com/nginx-proxy/docker-letsencrypt-nginx-proxy-companion/blob/v2.0.2/docs/Docker-Compose.md