supportsGrid.scss

$supportsGrid: TRUE;

@mixin supportsGrid() {
  @if $supportsGrid == TRUE {
    @supports (display: grid) {
      @content;
    }
  }
}

/* usage */
.thing {
  display: inline-block;
  @include supportsGrid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-column-gap: 24px;
  }
}