Plash

Plash can be used to set a website as your desktop wallpaper on Mac.

If you'd also want to set it as a Screensaver, look into https://github.com/liquidx/webviewscreensaver.

At this point you should have saved the animated wallpaper and extracted the .zip file into a safe location, that is hopefully not the Downloads folder so you won't accidentally remove it.

Download Plash.

Step 1: Add animated wallpaper

Click the menu bar item and go Add Website...

The other option Websites... opens a window where you can edit, remove and also add wallpapers.

Add the wallpaper folder that contains the index.html file.

Step 2: Confirm Plash starts on startup

In case it's not on by default, enable Launch at login.