This is a website with dark and light theme u can also use the js code in my repo to make ur own dark theme wensite. It also reads the custom theme from ur device and switches it automatically to that theme. basically if you are using dark theme then you will see dark theme website,And if u use light theme u will see light theme You can change the theme and it rembers your last saved theme.
https://siddharth1704.github.io/dark-theme/
---HOPE YOU LIKE IT-----