Hong Kong faces another 13 new Covid-19 cases on Friday, as officials revealed a fifth of the city’s population had signed up for the government’s mass coronavirus testing programme.The latest figures came on the day the government further relaxed social-distancing rules, including allowing four people to meet in public, and eat together in restaurants.As of this morning, more than 1.53 million people, or a fifth of the 7.5 million residents, had taken part in the mass testing programme, of…