Check for per vertex transparency when blending

[davepagurek]

Resolves #6539

Changes

• Checks (and caches) whether any per vertex colors include transparency
• Enables blending if that is true

Screenshots of the change

Before:

After:

Live: https://editor.p5js.org/davepagurek/sketches/QFQV0_K_E

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[Qianqianye]

Thanks @davepagurek. @acamposuribe, could you help review this PR since you opened the related issue? Thanks!

[davepagurek]

Tagging other WebGL stewards and contributors, let me know what you think! @aferriss, @aceslowman, @ShenpaiSharma, @ChihYungChang, @teragramgius, @JazerUCSB, @richardegil, @itsjoopark, @Gaurav-1306, @jeanetteandrews, @perminder-17

[aferriss]

Looks great! Thanks Dave!

[perminder-17]

Looks good to me. I think we are good to merge. Thanks.

[davepagurek]

Thanks everyone!