Looks like we need either:
- Text in aria-label attribute on the input field.
- OR; <label> element with text that wraps around the input field.
- OR; <label> element before the input field, associated via id/for. (This is what MediaWiki does, though broken due to T139427.)
In case of 2 or 3, the label could be hidden visually (as long as it's not ignored by screen readers).
The button currently carries no text or hint on what it's meant to be for assistive technology
<button class="pure-button pure-button-primary-progressive" type="submit"> <i class="sprite svg-search-icon"></i> </button>