q5-webgpu: Increased blendMode support

[quinton-ashley]

Here's a sketch that shows off the effect of every blend mode, this works in q5.js with the Canvas2D renderer as well.

https://editor.p5js.org/aleannab/sketches/r4VWTS7Cr
processing/p5.js#7228
https://p5js.org/reference/p5/blendMode/

When working on q5 WebGPU I followed this tutorial on how to implement some basic blend modes in v2.24.

https://webgpufundamentals.org/webgpu/lessons/webgpu-transparency.html

But I didn't add support for additional blend modes because they'd require editing each pipeline's fragment shader.

For now if you want to use other blend modes, stick to q5's Canvas2D renderer.

If anyone wants to implement increased blendMode support in WebGPU let me know.