Add list support for lerpColor like other color functions

[RandomGamingDev]

Resolves #6953

Changes:

Adds list support to the lerpColor like other color functions.
(I understand why this function doesn't support string based colors since you should know the actual value of the color when lerping between them, but adding list support is still definitely something that would be useful as seen in the referenced issue. However, if anyone thinks that adding string based color support to lerpColor as well would be preferred I'll add that to the PR.)

Screenshots of the change:

const red = [255, 0, 0];
const blue = [0, 255, 0];

function setup() {
  // These always worked
  fill(red);
  fill(blue);
  // This works now!
  lerpColor(red, blue, 0.5);
}

PR Checklist

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