THERE HAVE BEEN a few great trends for spring-summer 2021 so far—waistcoats, shrunken cardigans, Breton stripes and billowy summer dresses—just to name a few, but here are OUR VERY FAVOURITES: from the return of the silk satin midi skirt to the crisp and classic blue shirt (with or without stripes); preppy coordinated sweater sets and tiny tennis skirts; oversized trench coats and pretty silk scarves…