Including polka-dot and navy dresses similar to the actress’Credit: Frazer Harrison/WireImage / Amazon (1)Reese Witherspoon has a knack for making simple pieces look effortlessly cute — and her latest summer ’fit does just that. The actress posted an Instagram carousel with an assortment of photos, including one seated in a navy polka-dot dress. The dress’ sleeveless design works so well for lunch, errands, the office, or those days when you’re …