added paletteLerp

[RandomGamingDev]

Resolves #6959

Changes:

Add a function called paletteLerp() for lerping/interpolating between a list/palette of colors.

Screenshots of the change:

function setup() {
  createCanvas(400, 400);
}

function draw() {
  const palette = [color("red"), color("yellow"), color("green")];
  const lerp_color = paletteLerp(palette, (millis() / 2000) % 1);
  background(lerp_color);
}

PR Checklist

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

[RandomGamingDev]

Here's what the new version requested using color stops uses:

function setup() {
  createCanvas(400, 400);
}

function draw() {
  background(lerpPalette([
    ["white", 0],
    ["red", 0.05],
    ["green", 0.25],
    ["blue", 1]
  ], millis() / 10000 % 1));
}

[davepagurek]

This looks good! You mentioned on Discord potentially having a version that supports just an array of numbers for evenly-spaced stops, do you want me to wait before merging for that or do you want that to be a follow-up?

[davepagurek]

We talked on Discord and probably will end up doing another PR if we want to add a version with no stops, so I'll merge this now!