Improved jsdocs for withoutEnlargement and sequentialRead #972 (#992)

lib/input.js

@@ -256,6 +256,9 @@ function limitInputPixels (limit) {
 /**
  * An advanced setting that switches the libvips access method to `VIPS_ACCESS_SEQUENTIAL`.
  * This will reduce memory usage and can improve performance on some systems.
+ *
+ * The default behaviour *before* function call is `false`, meaning the libvips access method is not sequential.
+ *
  * @param {Boolean} [sequentialRead=true]
  * @returns {Sharp}
  */