By Uditha Jayasinghe and Dinuka Liyanawatte COLOMBO (Reuters) – Shops opened in Sri Lanka’s capital city Colombo amid tight security on Saturday – the first day after a state of emergency was declared to tackle growing unrest amid an unprecedented economic crisis. In an order late on Friday, President Gotabaya Rajapaksa invoked tough laws that allow the military to arrest and detain suspects. The state of emergency was necessary to protect public order and to maintain essential supplies and services, he said in a proclamation. Angered by shortages of fuel and other essential items, hundreds of…