message: fix(masthead): gray overlay showing up
  ### Description
  Gray overlay working again
  <img width="756" alt="Screen Shot 2021-02-10 at 17 06 46" src="https://user-images.githubusercontent.com/42848561/107565345-5cd19a80-6bc2-11eb-9827-241212d409a4.png">
diff: position: fixed;
  width: 100%;
  height: 100vh;
  - background-color: $ui-background;
  + background-color: rgba(22, 22, 22, 0.5);
  opacity: 1;
  transition: opacity $transition--expansion $carbon--standard-easing,
  background-color $transition--expansion $carbon--standard-easing;
  