File input

The file picker button is styled through ::file-selector-button, so it matches a secondary button without extra markup.

Class	Does what
`file-input`	Transparent field with a styled picker button

Basic

<label class="label">
  Attachment
  <input type="file" class="file-input" />
</label>

<label>
  Attachment
  <input type="file" />
</label>