This downloads a file that contains two different datapacks. One of them changes the maximum light level that mobs are allowed to spawn in to 7 in the overworld, like it used to be before Minecraft 1.18. The second one is more for fun and changes the maximum light level to 15, meaning that you'll be having hostile mobs spawning pretty much everywhere and there's not a whole lot that you'll be able to do about it. Don't just throw the entire thing into your game, it won't like that very much. Be nice to your game.

I may or may not update this in the future with more light levels, but since it's pretty easy to change this yourself I don't know if it's worth doing.