Enabling & Disabling Maintenance Mode (extend-maintenance) should mention Drush

Thanks for the issue! We definitely should mention the Drush commands in the topic about enable/disable of maintenance mode.
https://www.drupal.org/docs/user_guide/en/extend-maintenance.html

What we should do though is follow the style of other topics that mention Drush commands. I suggest looking at:
https://www.drupal.org/docs/user_guide/en/config-install.html

So what this patch needs:
- Site prerequisites section like in the config-install topic
- Under "Steps" the separation into using UI and using Drush, with same language as in the config-install topic. Please put the UI first. Keeping in mind this User Guide is mostly for newcomers to Drupal, they will mostly be more comfortable with the UI initially.

Thanks!

Actually what I think I'd suggest under Steps, is to add the line saying:

You can use the administrative interface or Drush to enable or disable maintenance mode.

Then I would add "using the administrative interface" to the first two headers that are already there, and add a new section at the bottom called "Enabling and disabling using Drush", that would just give the commands to enable/disable maintenance mode using Drush.

Would you like to make a new version @wturrell? If I don't see a response here in a few days, we'll find someone else to do it, so either way is fine. Thanks!

Here's a new patch...

This looks fine to me. Thanks Jennifer.

Thanks again for the issue and review! I committed this patch today, and translation group notifications are going out shortly with some other issues.