Issue 112: NGINX bot blocker

[aksm]

Resolves #112.

Steps for basic deployment (to be documented more thoroughly):

1. Uncomment variables starting MSMTP_ and NGXBLOCKER_ (start with both disabled, but fill in other appropriate variables.
2. docker-compose down && docker-compose pull && docker compose up -d.
3. Run install and setup scripts:
   1. docker exec -ti esmero-web bash -c "/usr/local/sbin/install-ngxblocker"
   2. Check output to make sure changes look ok.
   3. docker exec -ti esmero-web bash -c "/usr/local/sbin/install-ngxblocker -x"
   4. docker exec -ti esmero-web bash -c "/usr/local/sbin/setup-ngxblocker -v /etc/nginx/templates -e .copy"
   5. Check output to make sure changes look ok.
   6. docker exec -ti esmero-web bash -c "/usr/local/sbin/setup-ngxblocker -v /etc/nginx/templates -e .copy -x"
   7. Enable variables (if MSMTP_EMAIL is blank, email sending will be skipped):

      NGXBLOCKER_CRON_START=true
      NGXBLOCKER_ENABLE=true

   8. docker compose down && docker compose up -d
   9. docker exec -ti esmero-web bash -c "/docker-entrypoint.d/20-envsubst-on-templates.sh"
   10. docker exec -ti esmero-web bash -c "nginx -t"
   11. If output from above is:

       nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
       nginx: configuration file /etc/nginx/nginx.conf test is successful

       Run the following: docker exec -ti esmero-web bash -c "nginx -s reload"

       12. See Testing section ("Step 10") here: https://github.com/mitchellkrogza/nginx-ultimate-bad-bot-blocker