message: Button: update opacity for disabled
  primary
  secondary
  tertiary
  outline
diff: opacity: .4;
  }
  +.Button--lvl-primary[disabled],
  +.Button--lvl-secondary[disabled],
  +.Button--lvl-tertiary[disabled],
  +.Button--lvl-outline[disabled] {
  + opacity: .64;
  +}
  +
  .Button__before:not(:last-child) {
  margin-left: -4px;
  margin-right: 6px;
  