Piskel layered sprite game object

[blurymind]

Description

Currently have a layered sprite format, but when we save its layers get merged. This is a huge missed opportunity, as it could be used to create a much easier way to implement customisable sprites in a 2d game.

Solution suggested

Piskel sprites in Gdevelop can store layered data via the json piskel file format spec.
If we keep that json data we can potentially expose it the game engine and enable toggling visibility of sprite layers while the game is running.

This could be done by creating a new type of a game object - PiskelSprite?
Every time a layer is set to visible or not visible, the object must re-render the spritesheet from the piskel data, but also retain the frame state and do that so seamlessly, it is not seen by the player