feat: update namespace TypeScript declarations

PR-URL: stdlib-js#6275
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: stdlib-bot

lib/node_modules/@stdlib/array/base/docs/types/index.d.ts

@@ -85,6 +85,7 @@ import everyByRight = require( '@stdlib/array/base/every-by-right' );
 import fancySlice = require( '@stdlib/array/base/fancy-slice' );
 import fancySliceAssign = require( '@stdlib/array/base/fancy-slice-assign' );
 import fill = require( '@stdlib/array/base/fill' );
+import fillBy = require( '@stdlib/array/base/fill-by' );
 import filled = require( '@stdlib/array/base/filled' );
 import filledBy = require( '@stdlib/array/base/filled-by' );
 import filled2d = require( '@stdlib/array/base/filled2d' );
@@ -1947,6 +1948,38 @@ interface Namespace {
 	*/
 	fill: typeof fill;
 
+	/**
+	* Fills all elements within a portion of an array according to a provided callback function.
+	*
+	* @param x - input array
+	* @param start - starting index (inclusive)
+	* @param end - ending index (exclusive)
+	* @param fcn - callback function
+	* @param thisArg - callback function execution context
+	* @returns modified input array
+	*
+	* @example
+	* function fcn() {
+	*     return 4;
+	* }
+	*
+	* var x = [ 1, 2, 3 ];
+	*
+	* var out = ns.fillBy( x, 4, 0, 3 );
+	* // returns [ 4, 4, 4 ]
+	*
+	* @example
+	* function fcn() {
+	*     return 8;
+	* }
+	*
+	* var x = [ 1, 2, 3, 4, 5, 6 ];
+	*
+	* var out = ns.fillBy( x, 8, 0, 3 );
+	* // returns [ 8, 8, 8, 4, 5, 6 ]
+	*/
+	fillBy: typeof fillBy;
+
 	/**
 	* Returns a filled "generic" array.
 	*