By Iain Withers LONDON (Reuters) – The U.S. dollar resumed its slide on Monday as risk appetite across markets tentatively strengthened, supported by encouraging economic data and bets that the Federal Reserve will tighten policy at a slower pace. The dollar index – which tracks the greenback against six major rivals – is on track for its first monthly drop in five, as the safe-haven currency loses steam after a breakneck start to the year. The dollar index is on track for a more-than 1.5% drop in May – although it remains up about 6% on the year. It was last down 0.3% on the day at 101.440. T…