message: feat: remove uppercase text transform from buttons
diff: @include btn(light, $light, $white);
  .btn {
  - text-transform: uppercase;
  border: 0;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
  transition: all 0.4s; // stylelint-disable-line declaration-property-value-blacklist
  