Editorial: Markup Async Iterator string with emu-val (#14)

Author: arai-a

spec.html

@@ -560,7 +560,7 @@ <h1>AsyncIterator.prototype.find ( _predicate_ )</h1>
 
       <emu-clause id="sec-asynciteratorprototype-@@tostringtag">
         <h1>AsyncIterator.prototype [ @@toStringTag ]</h1>
-        <p>The initial value of the @@toStringTag property is the String value "Async Iterator".</p>
+        <p>The initial value of the @@toStringTag property is the String value *"Async Iterator"*.</p>
         <emu-note>
           <p>Unlike the @@toStringTag on most built-in classes, for web-compatibility reasons this property must be writable.</p>
         </emu-note>