Use separate animations for each atlas when using multiple textures in a sprite

**Is your feature request related to a problem? Please describe:**
When using multiple textures in a sprite, it's looking for the same animation in both atlases.

**Describe the solution you'd like:**
I'd like it to be optional, allowing to select different animations from each atlas.

**Describe alternatives you've considered:**
Maybe an alternative could be throwing a warning if the animation is not found in the secondary atlas, but allowing the game to run anyway.

**Additional context:**