Flexbox hidden

make attribute "hidden" work with flexbox.

HTML

<div>
  Normal shown
</div>
<div hidden>
  Normal hidden
</div>
<div class="flexbox">
  Flexbox shown
</div>
<div class="flexbox" hidden>
  Flexbox hidden
</div>

CSS

.flexbox{
  display: flex;
}

[hidden]{
  display:none;
}