message: Fix imports in customize-theme documentation
  Fix borders import naming and remove styles file extension.
diff: @@ -205,10 +205,10 @@ like this:
  import { extendTheme } from "@chakra-ui/core"
  // Global style overrides
  -import styles from "./styles.js"
  +import styles from "./styles"
  // Foundational style overrides
  -import border from "./foundations/borders"
  +import borders from "./foundations/borders"
  // Component style overrides
  import Button from "./components/button"
  