message: Update README.md to reflect current format API
  Related to
diff: @@ -13,7 +13,7 @@ for manipulating **JavaScript dates** in **a browser** & **Node.js**.
  ```js
  import {format, compareAsc} from 'date-fns/esm'
  -format(new Date(2014, 1, 11), 'MM/DD/YYYY')
  +format(new Date(2014, 1, 11), 'MM/dd/yyyy')
  //=> '02/11/2014'
  const dates = [new Date(1995, 6, 2), new Date(1987, 1, 11), new Date(1989, 6, 10)]
  