jquery.textSelection: Select sample text, if possible, when splitlines is true
completed by: Scimonster
mentors: Bartosz Dziewoński
Fix https://bugzilla.wikimedia.org/show_bug.cgi?id=70764 . Please read the bug report's description and comments to learn what needs to be done.
Students are required to read Wikimedia's general instructions at https://www.mediawiki.org/wiki/Google_Code-in_2014#Instructions_for_GCI_students first.