Docs: add avif and heif examples

lib/output.js

@@ -825,6 +825,16 @@ function tiff (options) {
  *
  * AVIF image sequences are not supported.
  *
+ * @example
+ * const data = await sharp(input)
+ *   .avif({ effort: 2 })
+ *   .toBuffer();
+ *
+ * @example
+ * const data = await sharp(input)
+ *   .avif({ lossless: true })
+ *   .toBuffer();
+ *
  * @since 0.27.0
  *
  * @param {Object} [options] - output options
@@ -842,9 +852,14 @@ function avif (options) {
 /**
  * Use these HEIF options for output image.
  *
- * Support for patent-encumbered HEIC images requires the use of a
+ * Support for patent-encumbered HEIC images using `hevc` compression requires the use of a
  * globally-installed libvips compiled with support for libheif, libde265 and x265.
  *
+ * @example
+ * const data = await sharp(input)
+ *   .heif({ compression: 'hevc' })
+ *   .toBuffer();
+ *
  * @since 0.23.0
  *
  * @param {Object} [options] - output options