Support for Drop-in config directories #267
Description
Right now, the config is /etc/lightdm/slick-greeter.conf. Many system settings also have a .d directory that allows the user to add extra files that are also loaded. In this case, it would likely be /etc/lightdm/slick-greeter.conf.d/<something>.conf or something of the like.
There are many use cases for this, for example with automation like Ansible, where it is very inconvenient to deal with a single file config, whereas drop-in directories would make it trivial to simply add a file instead of parsing the config.