Apply blendMode inside _drawPoints

[inaridarkfox4231]

The blend function was not applied inside _drawPoints, so let's apply it.

Resolves #6068

Changes:

Do _applyColorBlend() with strokeColor in _drawPoints().

Screenshots of the change:

sample code:

function setup(){
  createCanvas(400,400,WEBGL);
  background(0);
  blendMode(ADD);
  strokeWeight(100);

  stroke(255,0,0);
  point(0,0,0);
  stroke(0,0,255);
  point(50,0,0);
}

left : before, right : after

PR Checklist

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

I would also like to add a unit test later.

[davepagurek]

Thanks for catching and fixing this bug!

[inaridarkfox4231]

Thanks for merging! ('ω')
If I had noticed it earlier, I would have made it in time for 1.6.0, but it can't be helped...