feat: allow separator array to have different dtype

Signed-off-by: Athan <kgryte@gmail.com>

Author: kgryte

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

@@ -42,7 +42,7 @@ import { typedndarray } from '@stdlib/types/ndarray';
 * var v = gjoin( [ x, separator ] );
 * // returns '1,3,4,2'
 */
-declare function gjoin<T = unknown>( arrays: [ typedndarray<T>, typedndarray<T> ] ): string;
+declare function gjoin<T = unknown, U = unknown>( arrays: [ typedndarray<T>, typedndarray<U> ] ): string;
 
 
 // EXPORTS //