Add test on MessagesViewTest: clicking on a read receipt list emits the expected Event.

libraries/testtags/src/main/kotlin/io/element/android/libraries/testtags/TestTags.kt

@@ -63,6 +63,11 @@ object TestTags {
      */
     val messageBubble = TestTag("message_bubble")
 
+    /**
+     * Message Read Receipts.
+     */
+    val messageReadReceipts = TestTag("message_read_receipts")
+
     /**
      * Dialogs.
      */