Remove the `markdownify` call, and instead rely on Hugo's proper syntax; `{{% callout %}}` when we want to the content to be processed as Markdown.
This allows for stuff like:
{{% callout info %}}
##### I'm an info callout!
```css
.foo {
color: #fff;
}
```
{{< example >}}
<div class="alert alert-warning alert-dismissible fade show" role="alert">
<strong>Holy guacamole!</strong> You should check in on some of those fields below.
<button type="button" class="btn-close" data-dismiss="alert" aria-label="Close"></button>
</div>
{{< /example >}}
{{% /callout %}}
* Docs: (subjectively) nicer looking accordion example
the use of `.btn-link` currently just looks a bit odd, subjectively (as in v5 we now force the underline to always be there, while in v4 at least it was only on hover/focus).
`.btn-light` seems more fitting
* Add extra classes for nicer overall look
as suggested by @ysds
* Tweak accessibility note for accordions and optional keyboard interactions
