Write instructions for how to automate renewal with Docker

[bmw]

While Docker is a small percentage of our users, I don't think we have any good instructions here.

[viswanathct]

A reference for future users:

# This command stores the obtained test certificates and related files under the dir ./letsencrypt. The certificates are at ./letsencrypt/live/yourdomain.com
$ mkdir letsencrypt; docker run -p 80:80 -v $(pwd)/letsencrypt:/etc/letsencrypt certbot/certbot certonly --standalone --preferred-challenges http -n --agree-tos -m you@mail.com -d yourdomain.com --test-cert

[stale]

We've made a lot of changes to Certbot since this issue was opened. If you still have this issue with an up-to-date version of Certbot, can you please add a comment letting us know? This helps us to better see what issues are still affecting our users. If there is no activity in the next 30 days, this issue will be automatically closed.

[github-actions]

We've made a lot of changes to Certbot since this issue was opened. If you still have this issue with an up-to-date version of Certbot, can you please add a comment letting us know? This helps us to better see what issues are still affecting our users. If there is no activity in the next 30 days, this issue will be automatically closed.