Merge remote-tracking branch 'yamanoku/feature-hidden-until-found-values' into main

Author: richgerdes

normalize.css

@@ -342,8 +342,13 @@ template {
 
 /**
  * Add the correct display in IE 10.
+ * Except `hidden="until-found"`　because `content-visibility: hidden` is applied.
  */
 
 [hidden] {
   display: none;
 }
+
+[hidden="until-found"] {
+  display: revert;
+}

test.html

@@ -142,6 +142,7 @@ <h1>{{title}}</h1>
       <content></content>
     </template>
     <p hidden>This should be hidden</p>
+    <p hidden="until-found">This is not display none</p>
   </div>
 
   <h2 class="Test-describe"><code>a</code></h2>