Wrong css class for styling page dots in docs

flickity v2.2

`.dot` is stated in docs but code uses `.flickity-page-dot`.

https://flickity.metafizzy.co/style.html#page-dots

```css
/* position dots in carousel */
.flickity-page-dots {
bottom: 0px;
}
/* white circles */
.flickity-page-dots .dot {
width: 12px;
height: 12px;
opacity: 1;
background: transparent;
border: 2px solid white;
}
/* fill-in selected dot */
.flickity-page-dots .dot.is-selected {
background: white;
}
```

Start at the page-dots section of style.html, linked in the issue, and compare the documented selector with the class used by the code. Update the incorrect `.dot` reference so the documentation matches the actual page-dot styling selectors, then verify the rendered documentation shows the corrected example.

Written by the indexing model from the issue text.