docs: add documentation for toLocaleString method

Author: ahmad-kashkoush

lib/node_modules/@stdlib/array/fixed-endian-factory/README.md

@@ -908,6 +908,26 @@ var str = arr.join( 0 );
 // returns '10203'
 ```
 
+<a name="method-to-locale-string"></a>
+
+#### TypedArrayFE.prototype.toLocaleString( \[locales\[, options]] )
+
+Serializes an array as a locale-specific string.
+
+```javascript
+var Float64ArrayFE = fixedEndianFactory( 'float64' );
+
+var arr = new Float64ArrayFE( 'little-endian', [ 2000, 500, 8123, 12, 4212 ] );
+
+var str = arr.toLocaleString( 'en-US' );
+// returns '2,000,500,8,123,12,4,212'
+```
+
+The method supports the following arguments:
+
+-   **locales**: a string with a BCP 47 language tag or an array of such strings.
+-   **options**: configuration properties.
+
 </section>
 
 <!-- /.usage -->