[New Feature] Choose swww animation

[Frost-Phoenix]

First off, this project is really cool, thanks for the great tools.

So this is just an enhancement proposition.
It would be cool to be able to choose the animation with swww. Like having a line in the config for the animation to use when setting up a new wallpaper.

Don't know if this is something you are interested in, but it could add a little bit of customization.