Updated README for the playground
Updated README for the playground

hanhailong/practice-swift,nguyenantinhbk77/practice-swift,domenicosolazzo/practice-swift,hanhailong/practice-swift,nguyenantinhbk77/practice-swift,domenicosolazzo/practice-swift,nguyenantinhbk77/practice-swift,domenicosolazzo/practice-swift,hanhailong/practice-swift,domenicosolazzo/practice-swift,hanhailong/practice-swift,nguyenantinhbk77/practice-swift