function tint (tint) {
  this._setBackgroundColourOption('tint', tint);
  return this;
}
Tint the image using the provided colour.
An alpha channel may be present and will be unchanged by the operation.

@example
const output = await sharp(input)
  .tint({ r: 255, g: 240, b: 16 })
  .toBuffer();

@param {string|Object} tint - Parsed by the [color](https://www.npmjs.org/package/color) module.
@returns {Sharp}
@throws {Error} Invalid parameter