docs: Add CollapsedWave to showcase.md (#643)

migueltorrescosta

2023-12-20 be76da9e95b6744f4934280cb85504371ccc1244

 quartz/components/styles/legacyToc.scss

@@ -12,7 +12,7 @@
      margin: 0;
    }
  }
    

  & ul {
    list-style: none;
    margin: 0.5rem 1.25rem;