Apparently there is a brand new Web Standard now for making Browsers able to request Dark Mode Versions of Websites. And since it is new, its not publicly supported by the Browsers yet in most cases. But latest Firefox can already handle it with some about:config changes:
ui.systemUsesDarkTheme = 1 (may require you to actually make a new integer field)
browser.in-content.dark-mode = true
privacy.resistFingerprinting = false (Unsure if it’s a Firefox Bug or a Feature, but resisting Fingerprinting causes Dark Mode to fail, since requesting Dark Mode does help Sites with Fingerprinting)
While we are at it, here is some good security Advice for Browsers. ;)

GregTech, created by GregoriusT, is a Mod that completely overhauls Minecraft, adding numerous Machines and Materials, as well as adjusting Recipes for existing Items in order to make them fit with its System, and to make everything work well together, compatible and exploit-free whenever possible. GregTech is meant to extend the Game by making things much less overpowered, more reasonable and adding a lot of complex Machines, as well as generally useful Utility.

Bear’s Den, but note that they aren’t 100% child friendly (casual swearing etc), they also have some Modpacks. ;)

If you like this Mod then please help fund further development at my Patreon Page or via the new and improved Paypal Buttons down there:

More detailed Information can be found here.
If you used Paypal and aren’t on the List within 24 hours, message me instantly to make sure that nothing messed up. ^^

All the ways I can be contacted are listed in the Contact Information. If you just want to join my IRC Channel for Suggestions, Bugs and Support, it is #gt-dev on irc.esper.net.

If you want to find out some of my Plans for the Voxel Game I’m gonna be making after I’m fully done with GregTech-6, then check out this Link.

If you have interest in knowing what kind of person I am, then go here.