All themes are moved to `_theme` submodule, which will be shared with
other websites on hacks.guide.
Repository-specific files can be overlayed after the fact, such as
additional languages, custom JavaScript, progress table paths and the
like.
ALSO: Remove fading on dropdown menu click. This is also a bug on the actual upstream, when the cursor leaves the screen the menu disappears but the fading doesn't.
This causes things like the menu saying it's open when it's not and closed when open. I'm not dealing with an upstream bug.
