On mobile: focus on searchinput on offcanvas open

[tswfi]

Questions	Answers
Description?	On mobile view focus on the searchinput when the offcanvas search is shown. Also clear the search when the offcanvas is hidden
Type?	improvement
BC breaks?	no
Deprecations?	no
Fixed ticket?	Touches on issue #734 (the actual issue was already fixed before but when testing I noticed that this could be improved a bit)
Sponsor company
How to test?	On mobile view click on the search icon to get the offcanvas search to show, the focus should be on the input field and if a mobile phone is used the keyboard is shown. If input field contains text when closing the view then reopening the view should have the old search cleared and the focus again for a new search.

this replaces pr #796 . trying to rebase that thing was a nightmare