Docs: add .overflow-x-auto to CSS Grid nesting example at small bre…

…akpoints (#40928)

Co-authored-by: Julien Déramond <juderamond@gmail.com>

site/content/docs/5.3/layout/css-grid.md

@@ -149,7 +149,7 @@ Similar to our default grid system, our CSS Grid allows for easy nesting of `.gr
 In practice this allows for more complex and custom layouts when compared to our default grid system.
 
 {{< example class="bd-example-cssgrid" >}}
-<div class="grid text-center" style="--bs-columns: 3;">
+<div class="grid text-center overflow-x-auto" style="--bs-columns: 3;">
   <div>
     First auto-column
     <div class="grid">