fix #2674

Closes #2674

Merge request studip/studip!1878

resources/vue/components/courseware/layouts/CoursewareCompanionOverlay.vue

 <template>
+    <div class="cw-companion-overlay-wrapper">
         <div
             class="cw-companion-overlay"
             :class="[showCompanion ? 'cw-companion-overlay-in' : '', showCompanion ? '' : 'cw-companion-overlay-out', styleCompanion]"
-        :aria-hidden="!showCompanion"
+            aria-hidden="true"
         >
             <div class="cw-companion-overlay-content" v-html="msgCompanion"></div>
             <button class="cw-compantion-overlay-close" @click="hideCompanion"></button>
         </div>
+        <div
+            class="sr-only"
+            aria-live="polite"
+            role="log"
+        >
+            <p>{{ msgCompanion }}</p>
+        </div>
+    </div>
 </template>
 
 <script>