The BBC has unveiled a YouTube spin-off series of popular comedy show Things You Should Have Done as part of its wider digital strategy.Things You Should Have Done is a BBC Three sitcom created by internet personality, comedian and actress Lucia Keskin, known online as Chi with a C.It follows Keskin as a self-confessed "stay-at-home-daughter" who is left to fend for herself after her parents suddenly die in a car crash.She is then only able to a…