[idea] Add background for center, section etc

[Guray00]

Could be useful adding a background field in center and section to add more customization.

[estruyf]

I like the idea! Thanks @Guray00, for the suggestion! ❤️

[Guray00]

Thanks for your awesome work! I'm new in slidev themes, maybe I will be able to help in future!

[estruyf]

Cool! Just pushed out an update with this change. You are now able to set the background of the slide from the global configuration, or per slide.

[Guray00]

Thanks, working!