message: minor font updates from ben
diff: --code-background: #f5f7fa;
  --code-color: var(--text-color--dark);
  --code-font-family: "SFMono-Regular", "Roboto Mono", Consolas, "Liberation Mono", Menlo, Courier, monospace;
  - --font-family: system-ui, sans-serif;
  + --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI emoji";
  --header-height: 56px;
  --heading-font-family: var(--font-family);
  --line-rule-color: #edf2f6;
  @@ -121,10 +121,24 @@ h5,
  h6 {
  color: var(--text-color--dark);
  font-family: var(--heading-font-family);
  - letter-spacing: -0.03em;
  + letter-spacing: 0;
  line-height: 1.1;
  padding-top: 2em;
  }
  +h1,
  +h2,
  +h3,
  +h4,
  +h5,
  +h6,
  +h1 a,
  +h2 a,
  +h3 a,
  +h4 a,
  +h5 a,
  +h6 a {
  + font-weight: 600;
  +}
  h1 {
  font-size: 3.5rem;
  