message: make activity feed media item buttons easier to see in dark mode
diff: left: 0
  .-prev, .-next
  - theme-prop('background-color', 'darker')
  + theme-prop('background-color', 'bg-subtle')
  + theme-prop('color', 'fg')
  display: none
  position: absolute
  top: 50%
  height: 80px
  - width: $grid-gutter-width
  + width: $grid-gutter-width * 0.75
  line-height: @height
  margin-top: -(@height / 2)
  - color: $white
  text-align: center
  z-index: 2
  user-select: none
  &:hover
  - theme-prop('color', 'highlight')
  + theme-prop('color', 'link')
  @media $media-sm-up
  display: block
  .-prev
  - left: -($-item-padding-container + $grid-gutter-width)
  + left: -($-item-padding-container + $grid-gutter-width * 0.75)
  border-top-left-radius: $border-radius-base
  border-bottom-left-radius: $border-radius-base
  .-next
  - right: -($-item-padding-container + $grid-gutter-width)
  + right: -($-item-padding-container + $grid-gutter-width * 0.75)
  border-top-right-radius: $border-radius-base
  border-bottom-right-radius: $border-radius-base
  