Xeltalliv/clippingblending: Fix canvas alpha compatibility and other changes

[Xeltalliv]

This:

• Fixes compatibility with canvas having alpha, without changing behavior of any old projects compared to how they used to work (at least in theory).
• Sorts out long standing issue of some blending modes working incorrectly, by deprecating old block and making a new one, where everything is done in a corrected and clean way.
• Adds new blending modes, to provide proper solutions to what was done through bugs.
• Adds API, so that Shaded extension can be compatible with this extension, without the need for maintaining a custom fork of it.
• Adds a label explaining why there is sometimes no blocks in the palette.
  

[SharkPool-SP]

Instead of the function for getting the drawable you could just use the Drawable class in renderer.exports

[Xeltalliv]

Um, that's exactly what I did

extensions/extensions/Xeltalliv/clippingblending.js

Line 37 in e694b07

let Drawable = renderer?.exports?.Drawable || getDrawable();

but I kept the old one as a fallback, in case this extension was used in some obscure outdated turbowarp mods without renderer.exports.

[SharkPool-SP]

oh didnt even see that mb, was looking over it on my phone lol

[SharkPool-SP]

Yuri has to approve because she made requests. I can’t merge :(

resolved probably