Add "dark mode" button in this website!!

Created by: 4kashyadav

I am adding the button named "D" , if we click on that then the dark mode will be activated. Dark mode is here to help with this, making the screen easier to see in low lighting such as in the night or early morning. It can be a lot easier on the eyes, causing less strain and is better in the long run. So can you assign me this because I want to contribute in this.