Add orderByNullsLast docs.

Author: yajra

documentation.md

@@ -46,6 +46,7 @@
 	- [Manual Order](/docs/laravel-datatables/{{version}}/manual-order)
 	- [Order Column](/docs/laravel-datatables/{{version}}/order-column)
 	- [Order Columns](/docs/laravel-datatables/{{version}}/order-columns)
+	- [Order Nulls Last](/docs/laravel-datatables/{{version}}/order-by-nulls-last)
 - Utilities
 	- [XSS filtering](/docs/laravel-datatables/{{version}}/xss)
 	- [Blacklist Columns](/docs/laravel-datatables/{{version}}/blacklist)

order-by-nulls-last.md

@@ -0,0 +1,15 @@
+# Order by NULLS LAST
+
+This api will set Datatables to perform ordering with `NULLS LAST` option.
+
+```php
+use Datatables;
+
+Route::get('user-data', function() {
+	$model = App\User::query();
+
+	return Datatables::eloquent($model)
+			->orderByNullsLast()
+			->make(true);
+});
+```