LONDON (Reuters) -Workers at British packaging group DS Smith, whose customers include Amazon, have voted overwhelmingly to go on strike in a dispute over pay, their union said on Monday. The industrial action could start as soon as the end of this month, the GMB union said. GMB, which represents 1,000 workers at the London-listed company, said 93% of the workers had voted for strikes. “We are disappointed with the vote for industrial action, particularly at a crucial time for all of our customers,” a DS Smith spokesperson said. The union said a strike at DS Smith could have “serious implicati…