PayPal is planning a $750 million investment in MercadoLibre, the dominant e-commerce and fintech player across Latin America. Founded in 1999, just four years after Amazon made its debut, MercadoLibre serves 267.4 million users as of 2018, according to Statista, and moved 150.1 million shipments in 2017 plus another 105.3 million through the first six…