Update docker.md

Update docker.md

1. I don't know if you're supposed to do something other than enter `$EDITOR ./docker-compose.yml` into terminal, but when I did that it gave a permission error, so I just used nano. Same with `.env`.

2. Newer versions of Docker Compose use the command `docker compose`, not `docker-compose`.

3. Grepping the password from logs was not working. I looked at the full logs, and I didn't see anything about a password. I added how to set a custom password. Maybe the grepping part should be removed or changed to make it work.