Accessibility: accessible widget search

[ramiy]

The widget search is not accessible. It should either use role="search" or type="search".

In addition, the input field should have a label for screen readers. We hide the label for regular users using class="screen-reader-text", this way only screen readers "see" it.

Ref: https://www.w3.org/TR/html-aria/

[ramiy]

@arielk Please review the PR.

[ramiy]

@kobizz, @matipojo, @joshmarom

on the same principle, when we define Controls with 'show_label' => false argument, the Label should not be removed, it should have class="screen-reader-text". This way screen readers "see" it but normal users don't.