Make `draw_image` support all blend modes

[karl-zylinski]

Asesprite has layers that can have different blend modes. Currently draw_image just does some "additive" blending. The atlas builder would need to know the blend type for each layer and make sure to apply all the layers in the correct order.

[blob1807]

I don't mind going about adding this, but it'll add about 400-500 loc. So just wanna check it's something you'd still be interested in adding.

There's also the problem of Asesprite's implementation of setting saturation is bugged & whether to adhere to it or use a fixed version. For odin-aseprite I have a config toggle to switch between them.

[karl-zylinski]

Please, have a go at it!

I actually ended up using Aseprite CLI for a project because I didn't have time to fix this.

For the broken feature, a flag sounds good