Do not install. It is a 1-to-1 clone of the original and trusted Dark Reader plugin. The only reason why someone would make this plugin is for stealing user data, bitcoin mining, or some other shady stuff you don't want on your computer.

It doesn't look anything like what you see in the screenshot. This extension calls itself "Dark Mode" in the add-ons section, then calls itself "Lights Off - Free" in the addons manager, but in the toolbar it looks exactly like "Dark Reader" which is a more popular addon from a different creator.
I wanted dark websites, not shady extensions!