Shares of Playtika, one of the world’s hottest mobile gaming startups, soared about 17 percent on the first day of trading Friday, after the company raised nearly $2 billion in a huge initial public offering on the Nasdaq Stock Market. The Israel-based maker of casino-style apps like Slotomania and World Series of Poker has more than 30 million active monthly users globally and generates about 70 percent of its business from gamers based in the United States. The biggest winners in the l