fix(header-search): Disable page zoom on search focus on smaller iOS devices

[jtomaszewski]

On iOS the search input has to be at least 16px large, otherwise it will needlessly trigger page zoom once the input is focused.

• https://stackoverflow.com/questions/2989263/disable-auto-zoom-in-input-text-tag-safari-on-iphone
• https://www.warrenchandler.com/2019/04/02/stop-iphones-from-zooming-in-on-form-fields/

[martasiewierska]

Thank you a lot for your contribution. PR was merged.