docs: document sort order

Signed-off-by: Athan <[email protected]>

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/ndarray/gsorthp/README.md

@@ -72,6 +72,7 @@ The function has the following parameters:
 ## Notes
 
 -   The input ndarray is sorted **in-place** (i.e., the input ndarray is **mutated**).
+-   When the sort order is less than zero, the input ndarray is sorted in **decreasing** order. When the sort order is greater than zero, the input ndarray is sorted in **increasing** order. When the sort order is equal to zero, the input ndarray is left unchanged.
 
 </section>