As we move forward with DarkMode, we're creating an extension. The skeleton (CI rules + base files + linting) should have happened on {T221877}
This ticket defines the base behavior of the extension itself, to enable the switching for users:
[] Create a hidden preference that will be used to judge whether a user enabled DarkMode or not
[] ~~(As we are testing this) Add a cookie check for logged out users~~ !![waiting to find out if we are doing this]!!
[] PHP: In the page rendering hook a condition whereby if the preference (or cookie) are true, the html class is added to <body> and the CSS style modules are attached
[] PHP: Allow for a temporary override of the cookie/preference state through the URL parameter `?usedarkmode=1`. This should temporarily override (not actively change the value) of the cookie or preference for the immediate page load.
[] JS: Add basic toggle while we wait for the official design. NOTE: The toggle should lazy-load any necessary JS modules.