Update extended-search mode section of README
Update extended-search mode section of README

tomfitzhenry/pkg-fzf,stuha/wbr-zsh,pokey/fzf,janlazo/fzf,noscript/fzf,junegunn/fzf,wilywampa/fzf,junegunn/fzf,tomfitzhenry/pkg-fzf,mjwestcott/fzf,qiemem/fzf,mjwestcott/fzf,qiemem/fzf,qiemem/fzf,pokey/fzf,me-and/fzf,tomfitzhenry/pkg-fzf,me-and/fzf,junegunn/fzf,noscript/fzf,noscript/fzf,mjwestcott/fzf,infokiller/fzf,me-and/fzf,infokiller/fzf,janlazo/fzf,janlazo/fzf,pokey/fzf,lululau/fzf,wilywampa/fzf,lululau/fzf,infokiller/fzf,lululau/fzf,wilywampa/fzf