Create scss-docs shortcode to get some snippets from the Scs… (#30502)

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

scss/forms/_validation.scss

@@ -5,6 +5,8 @@
 // pseudo-classes but also includes `.is-invalid` and `.is-valid` classes for
 // server-side validation.
 
+// scss-docs-start form-validation-states-loop
 @each $state, $data in $form-validation-states {
   @include form-validation-state($state, map-get($data, color), map-get($data, icon));
 }
+// scss-docs-end form-validation-states-loop