feat(modal): add border (#20984)

* feat(modal): add border

* fix: enable-dialog-element style precedence

---------

Co-authored-by: Nikhil Tomar <63502271+2nikhiltom@users.noreply.github.com>

Author: maradwan26

packages/react/src/components/Modal/Modal.stories.scss

@@ -16,12 +16,12 @@
 @use '@carbon/react/scss/components/multiselect/multiselect';
 
 .preview-modal {
+  @include dialog.dialog();
   @include modal.modal(
     $enable-experimental-focus-wrap-without-sentinels: true,
     $enable-focus-wrap-without-sentinels: true,
     $enable-dialog-element: true
   );
-  @include dialog.dialog();
   @include text-input.text-input();
   @include select.select();
   @include dropdown.dropdown();

packages/styles/scss/components/modal/_modal.scss

@@ -96,6 +96,7 @@
   .#{$prefix}--modal-container {
     position: fixed;
     display: grid;
+    border: 1px solid $border-subtle-01;
     background-color: $layer;
     grid-template-columns: 100%;
     grid-template-rows: auto 1fr auto;