add modal screen reader description styling

Author: Sine Jespersen

src/styles/scss/shared.scss

@@ -23,6 +23,16 @@
   overflow: hidden;
 }
 
+.modal-screen-reader-description {
+  position: absolute;
+  clip: rect(1px, 1px, 1px, 1px);
+  padding: 0;
+  border: 0;
+  height: 1px;
+  width: 1px;
+  overflow: hidden;
+}
+
 .modal-btn-close {
   background-color: $c-global-primary;
   position: fixed;