Reddit mascot rings the opening bell, at the New York Stock Exchange (NYSE) in New York City, U.S., March 21, 2024.Brendan McDermid | ReutersReddit shares rose 11% in extended trading on Thursday on the social media company's inclusion in the S&P 500.The company will join the index on Aug 18, replacing AvalonBay Communities, according to a release from S&P Dow Jones Indices.Companies often see their stocks climb when they're added to major indexes because fund managers who trace the benchmarks h...