[Suggestion] add flex-wrap

[sobolevn]

When dealing with .grid and .cells it seems reasonable to me to add flex-wrap: wrap to prevent the situation like this:

code:

<div class="grid">

  <%= for v in [1, 2, 3, 4, 5] %>
  <div class="cell -4of12">
    <div class="card">...</div>
  </div>
  <% end %>
</div>

After a fix it will become something like this: