Vercel, a startup that helps companies develop web and artificial intelligence applications in the cloud, is raising hundreds of millions of dollars at a valuation of about $9 billion, according to people familiar with the matter. Accel, an early venture capital backer of companies like Slack and Dropbox Inc., is leading the investment, the people said, asking not to be named discussing private information. A spokesperson for Vercel didn’t respond to a request for comment. Accel declined to comm...