message: constants: supported themes for separators and tap highlights
diff: +@import "scheme.css";
  +
  :root {
  /* fonts */
  --font-ios: -apple-system, Helvetica Neue, Arial;
  --font-common: -apple-system, Roboto, Helvetica Neue, Arial;
  /* borders */
  - --ios-top-border: linear-gradient(to bottom, var(--separator) 50%, transparent 50%);
  - --ios-bottom-border: linear-gradient(to top, var(--separator) 50%, transparent 50%);
  - --ios-left-border: linear-gradient(to right, var(--separator) 50%, transparent 50%);
  - --ios-right-border: linear-gradient(to left, var(--separator) 50%, transparent 50%);
  + --ios-top-border: linear-gradient(to bottom, var(--separator_common) 50%, transparent 50%);
  + --ios-bottom-border: linear-gradient(to top, var(--separator_common) 50%, transparent 50%);
  + --ios-left-border: linear-gradient(to right, var(--separator_common) 50%, transparent 50%);
  + --ios-right-border: linear-gradient(to left, var(--separator_common) 50%, transparent 50%);
  /* easings */
  --ios-easing: cubic-bezier(.36, .66, .04, 1);
  --separator: rgba(0, 0, 0, .12);
  --placeholder-background: rgba(0, 28, 61, .08);
  --placeholder-foreground: rgba(0, 36, 77, .25);
  - --ios-active-color: #d9d9d9;
  - --android-active-color: #f0f1f3;
  + --ios-active-color: var(--separator_common);
  + --android-active-color: var(--separator_common);
  }
  