By Pavel Polityuk, Max Hunder and Simon Lewis KREMENCHUK (Reuters) -Western nations on Monday pledged unwavering support for Ukraine in the war with Russia, including more sanctions on Moscow and air-defence systems, as Ukrainian officials said two Russian missiles struck a shopping centre, killing at least 10 people. Leaders of the Group of Seven major democracies, meeting at a German alpine resort, said they would keep sanctions on Russia for as long as necessary and intensify international pressure on President Vladimir Putin’s government and its ally Belarus. “Imagine if we allowed Putin t…