(Reuters) - Britain's Royal Mail has proposed a three-year pay deal to the Communication Workers Union (CWU) and wants to have detailed talks with its largest union, the company said on Twitter on Friday.The company, which was dogged by the threat of strike action over the Christmas period, had said on Thursday that the CWU was preparing another strike ballot."We have today put forward a proposal to CWU, including a three-year pay deal," Royal Mail said in Friday's tweet."We want to get into..