/// Helper mixin to for the associated styles with position: sticky;
///
/// @param {Number} $z-index - The z-index property value.
/// @param {Number} $top - The top property value.
/// @param {Number} $left - The left property value.
///
/// @group Utilities
@mixin sticky($z-index: 999, $top: 0, $left: null) {
  position: sticky;
  top: #{$top};

  @if $left {
    left: #{$left};
  }

  z-index: #{$z-index};
}