Supporters of Javier Milei celebrated in the streets of Buenos Aires on Sunday after he won Argentina's presidential election runoff.Outside his party's headquarters, a hotel in downtown Buenos Aires, a full-on party kicked off with supporters singing and waving flags.With 99.4% of votes tallied in the presidential runoff, Milei had 55.7% and Economy Minister Sergio Massa 44.3%, according to Argentina's electoral authority. Source: AP