message: Improve marketmaker page styles
diff: .section-title {
  margin: 0 auto 1em;
  - max-width: 500px;
  + max-width: 20em;
  font-style: normal;
  line-height: 1em;
  font-size: 30px;
  button {
  @include ff-light;
  + letter-spacing: 0.05rem;
  }
  .devVersionLink {
  }
  }
  +
  +@include media-mobile {
  + .mm-promo-page {
  + .promoHeader {
  + padding: 1em;
  + }
  + }
  +
  + .installExtensionBody {
  + button,
  + .devVersionLink {
  + font-size: 0.9em;
  + }
  + }
  +}
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