feat(modal): add visually-hidden styles for dialog dismissHelpers

Author: marissahuysentruyt

packages/modal/src/modal.css

@@ -24,3 +24,16 @@
 .modal {
     overflow: visible;
 }
+
+.visually-hidden {
+    border: 0;
+    clip: rect(0, 0, 0, 0);
+    clip-path: inset(50%);
+    height: 1px;
+    margin: 0 -1px -1px 0;
+    overflow: hidden;
+    padding: 0;
+    position: absolute;
+    width: 1px;
+    white-space: nowrap;
+}