grid-dnd breaks animated background

[TRusselo]

Checklist:

• [ ] I updated to the latest version available
• [ ] I cleared the cache of my browser

Release with the issue: 2020.12.1 Last working release (if known):

Browser and Operating System: Chrome Windows

Description of problem: https://github.com/Villhellm/lovelace-animated-background Animated background gets blocked by background color

Javascript errors shown in the web inspector (if applicable):

![image](https://user-images.githubusercontent.com/1154815/102578909-884f7180-40b8-11eb-9f30-6bf494cde41c.png)


**Additional information:**
Followed instructions from youtube video 
https://www.youtube.com/watch?v=O2xvK4MR7eY