Add reference to MDN picture tag

Author: stevepiercy

docs/classic-ui/images.md

@@ -285,7 +285,7 @@ To access image scales, which are normally not accessible to the current user, o
 
 ## Responsive image support
 
-Plone supports the generation of `picture` tags with `srcset`s for image optimization.
+Plone supports the generation of [`picture`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/picture) tags with `srcset`s for image optimization.
 Additionally, you can define [media queries](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_media_queries/Using_media_queries) for [art direction](classic-ui-images-responsive-image-support-art-direction) and further optimization.
 
 The configuration allows you to define different `picture` variants, such as `Large`, `Medium`, or `Small`.