Shares of Datadog (DDOG 15.12%) charged sharply higher Thursday. As of 10:53 a.m. ET, the stock was up 13.1%.The catalyst that sent the cloud monitoring, analytics, and security company soaring was the revelation that the stock will be joining the most widely followed stock market index in the U.S. An important nodIn a press release that dropped after the market closed on Wednesday, S&P Dow Jones Indices announced that Datadog would be added to the S&P 500 (^GSPC 0.84%) before the start of trading on July 9 ...