fix: increase type specificity

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

Author: kgryte

lib/node_modules/@stdlib/blas/ext/join/docs/types/index.d.ts

@@ -35,7 +35,7 @@ type Separator<U> = genericndarray<U> | U;
 /**
 * Output array.
 */
-type OutputArray = genericndarray<any>;
+type OutputArray<T> = genericndarray<T>;
 
 /**
 * Interface defining "base" options.
@@ -85,7 +85,7 @@ interface Join {
 	* var idx = y.get();
 	* // returns '1,2,3'
 	*/
-	<T = unknown, U=unknown>( x: InputArray<T>, separator: Separator<U>, options?: Options ): OutputArray;
+	<T = unknown, U=unknown>( x: InputArray<T>, separator: Separator<U>, options?: Options ): OutputArray<string>;
 
 	/**
 	* Joins elements of an input ndarray using a specified separator along an ndarray dimension and assigns results to a provided output ndarray.
@@ -116,7 +116,7 @@ interface Join {
 	* var idx = out.get();
 	* // returns '1,2,3'
 	*/
-	assign<T = unknown, U = unknown, V extends OutputArray = OutputArray>( x: InputArray<T>, Separator: Separator<U>, out: V, options?: BaseOptions ): V;
+	assign<T = unknown, U = unknown, V extends OutputArray<string> = OutputArray<string>>( x: InputArray<T>, Separator: Separator<U>, out: V, options?: BaseOptions ): V;
 }
 
 /**