docs: add note

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

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/ndarray/gfind-index/docs/types/index.d.ts

@@ -69,6 +69,10 @@ type Predicate<T, U, ThisArg> = Nullary<ThisArg> | Unary<T, ThisArg> | Binary<T,
 /**
 * Returns the index of the first element in a one-dimensional ndarray which passes a test implemented by a predicate function.
 *
+* ## Notes
+*
+* -   If no element passes a test implemented by a predicate function, the function returns `-1`.
+*
 * @param arrays - array-like object containing an input ndarray
 * @param clbk - predicate function
 * @param thisArg - predicate function execution context