That assigns the class `centered-chunk` **only to the output div**, which is what pkgdown renders as `<div class="output centered-chunk">...</div>`.

---

## ✅ 2. Add this to your `extra.css`

This CSS covers both **pkgdown vignettes** and **standalone HTML** output.

```css
/* ---- Centering for custom output chunks ---- */

/* Works in normal R Markdown (no pkgdown) */
.centered-chunk {
  text-align: center;
}

/* Ensure tables and images are centered */
.centered-chunk table {
  margin-left: auto !important;
  margin-right: auto !important;
}

.centered-chunk img {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

/* Works in pkgdown vignette rendering */
div.output.centered-chunk {
  display: flex;
  justify-content: center;
}

div.output.centered-chunk table,
div.output.centered-chunk img {
  margin-left: auto !important;
  margin-right: auto !important;
}