@mixin nav-divider($bg: $black-divider) {
  background-color: $bg;
  height: 1px;
  margin: $spacer-sm 0;
  overflow: hidden;
}

@mixin nav-divider($bg: $black-divider, $margin-y: $spacer-sm) {
  background-color: $bg;
  height: 1px;
  margin: $margin-y 0;
  overflow: hidden;
}

Allow to customize vertical margin of `nav-divider` mixin
Allow to customize vertical margin of `nav-divider` mixin
