This morning Alpaca, a startup that helps other companies add commission-free equities trading to their own products, announced a $10 million Series A. The new capital event was led by Portag3, and included prior investors Social Leverage, Spark Capital, Fathom Capital and Abstract Ventures. The company previously raised a $6 million pre-seed and $6 million seed round that TechCrunch covered last November. Alpaca is a company that has cropped up in our coverage of the startup and private capital markets recently, adding its perspective to our discussion of API-powered startups…