Add more sprite attribute animations

[paulossilva]

The most common way of animating sprites in the ZX Spectrum Next is by changing its pattern every few frames to make the movement illusion of an item on screen. Other ways of doing animation is by changing other sprite attributes, like palette offset (or by changing a single palette index), rotation, scale and mirroring.

It would be really useful to add animation support considering these sprite attributes. This would help new and seasoned developers to try out and discover new ways of animating sprites, which would be a much harder/slower process to try out by coding otherwise.

Consider that some animations take more the two frames to complete. For example, an explosion could take 3, 4 or even up to 5 frames to displayed in its entirety.

Thus, ideally, a sprite animation tool would need to support:

1. A configurable number of frames (this feature is already available on your animation tool)
2. To optionally set a few sprite attributes on a frame basis. For instance, change a palette colour index in the second frame, alongside changing its pattern, or even rotate it.
3. To apply overall options to the animation (I think the ones you have already implemented are great, so leave it as it is)

Possible examples of animation changing the palette offset/index is to illustrate a player death by electrical shock or a spaceship collecting a power-up.

[paulossilva]

I noticed that you are using the word Frames in the UI to refer to both the animation frame and pattern number used in that frame. You might need to change that and split up both numbers, so that one could define the pattern number 12 in the frame number 1 and so on. It will make more sense when adding relative sprites to the mix as you could change an anchor and/or relative sprite pattern in each frame.