Show number of matches when finding in page

(available only in API16+)

Original feature request:
https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom&TicketID=7662758

Co-authored-by: dbrant <dbrant@wikimedia.org>
Change-Id: If18fccc36ae0eac336f8c9988d681f77b5ef0f53