Today, London-based singer-songwriter and producer Gareth Donkin has unwrapped “This Winter,” a jubilant holiday original inspired by the cozy spirit of the season. Arriving with a playful music video, the new single showcases Donkin’s distinct sense of melody and his honeyed falsetto, nodding to classics like Wham!’s “Last Christmas” over a rich blend of synths, electric guitar, percussion and sleigh …