(Reuters) -Russia and Ukraine will sign a deal on Friday to reopen Ukraine’s Black Sea ports for grain exports, Turkey said, raising hopes that an international food crisis caused by Russia’s invasion could be eased. Ukraine and Russia, both among the world’s biggest exporters of food, did not immediately confirm Thursday’s announcement by the office of the Turkish presidency. But in a late night video address Ukrainian President Volodymyr Zelenskiy hinted his country’s Black Sea ports could soon be unblocked. The blockade by Russia’s Black Sea fleet has reduced supplies to markets around the …