Captions, a startup that uses artificial intelligence to let people create and edit videos, has raised a new funding round from a star-studded list of investors, vaulting its valuation to $500 million.The startup raised $60 million in a deal led by Index Ventures, the company plans to announce Tuesday. That brings its total funding raised to $100 million. Other investors in the round include previous backers Kleiner Perkins, Andreessen Horowitz and Sequoia Capital, as well as new ones, like acto...