Fix Drupal always getting server IP address for requests

[geerlingguy]

Apparently I forgot to configure the proxy settings from Nginx (since it's used for caching and PHP is running on internal port 81), so all requests look like they're coming from the same IP address, 104.236.203.61.

This causes two major problems:

1. I can't log in anywhere because Drupal's flood controls block any login attempts due to bad actors filling up the flood table for that IP.
2. Users can't comment because it looks like all comments come from the same IP, so that IP has been blocked by CleanTalk.

[geerlingguy]

Looks like I could use something like the following in settings.php:

<?php
$settings['reverse_proxy'] = TRUE;
$settings['reverse_proxy_addresses'] = ['1.2.3.4', ...];

[geerlingguy]

Worked! I added that to my settings.local.php. Adding a note about it in the repo example.