Docs: add more examples (composite, greyscale, tint)

lib/colour.js

@@ -19,6 +19,11 @@ const colourspace = {
  * Tint the image using the provided chroma while preserving the image luminance.
  * 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} rgb - parsed by the [color](https://www.npmjs.org/package/color) module to extract chroma values.
  * @returns {Sharp}
  * @throws {Error} Invalid parameter
@@ -37,6 +42,10 @@ function tint (rgb) {
  * This may be overridden by other sharp operations such as `toColourspace('b-w')`,
  * which will produce an output image containing one color channel.
  * An alpha channel may be present, and will be unchanged by the operation.
+ *
+ * @example
+ * const output = await sharp(input).greyscale().toBuffer();
+ *
  * @param {Boolean} [greyscale=true]
  * @returns {Sharp}
  */