message: feat: Sass helper to box-shadow inset
diff: @mixin use-focus-shadow($outer-color) {
  box-shadow: 0 0 0 #{ to-rem(4) } #{ $outer-color };
  }
  +
  +@mixin use-focus-shadow-inset($outer-color) {
  + box-shadow: 0 0 0 #{ to-rem(4) } #{ $outer-color } inset;
  +}
  