Billionaire Mukesh Ambani moved a step closer to creating an e-commerce giant for India, unveiling plans to set up a $24 billion digital-services holding company that would become the main vehicle in his ambition to dominate the country’s internet shopping space.   The board of Ambani’s Reliance Industries Ltd. approved a proposal to plow 1.08 trillion rupees ($15 billion) into the fully owned subsidiary, which will in turn invest that amount in Reliance Jio Infocomm Ltd., the conglomerate’s telecommunications venture. A series of capital transfers would make Jio, which already has capital of 650 billion rupees, almost debt free by March 2020, the parent said Oct. 25.