message: fix(playground): match code background to designs
diff: --playground-btn-icon-hover-background: rgba(67, 79, 93, 0.5);
  --playground-separator-color: var(--c-carbon-70);
  +
  + --playground-code-background: rgb(22, 29, 37);
  }
  .playground {
  * @prop --playground-btn-icon-color The text color of the button icon in the toolbar.
  * @prop --playground-btn-icon-hover-background The background color of the button icon in the toolbar when hovered.
  * @prop --playground-separator-color The color of the separator/border in the toolbar.
  + * @prop --playground-code-background The background color of the code block when expanded.
  */
  --playground-btn-color: var(--c-indigo-90);
  --playground-btn-selected-color: var(--c-blue-90);
  --playground-btn-icon-hover-background: var(--c-indigo-20);
  --playground-btn-icon-color: var(--c-indigo-80);
  --playground-separator-color: var(--c-indigo-30);
  + --playground-code-background: var(--c-indigo-10);
  overflow: hidden;
  }
  height: initial;
  margin-top: 16px;
  }
  +
  +/* overwrite existing Docusaurus style */
  +.playground__code-block pre[class*='language-'] {
  + background-color: var(--playground-code-background);
  +}
  \ No newline at end of file
  