A BitGo logo during a Bitcoin conference in Miami.Photographer: Eva Marie Uzcategui/BloombergBitGo Holdings Inc. has filed for an initial public offering in the US, adding to an active market for digital assets.The crypto custody firm had net income of $12.6 million on revenue of $4.19 billion for the first six months of the year, compared with net income of $30.9 million on revenue of $1.12 billion a year earlier, according to its filing Friday with the US Securities and Exchange Commission....