Tabsets fail if Header 1 used

[al-obrien]

When adding a Header 1, tabsets fail to render in the previewed/deployed pkgdown site. Maybe I am silly and have simply ignored advice never to use a Header 1 in pkgdown articles?

My session (excuse the old R, its legacy code)

• R version: 3.6.3
• pkgdown: 2.0.9

No header 1 - Tabs work

---
title: "test"
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = FALSE,
  comment = "#>"
)
```

## THIS IS A HEADER 2

ASDFASDF


### Tabset with pills {.tabset .tabset-pills}

#### Tab 12

blablablabla

```r
1 + 1
```

Should be "cool" heading below

##### cool

Stuff

#### Tab 2

blop

Header 1 - Tabs fail

---
title: "test"
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = FALSE,
  comment = "#>"
)
```

# THIS IS A HEADER 1

ASDFASDF


### Tabset with pills {.tabset .tabset-pills}

#### Tab 12

blablablabla

```r
1 + 1
```

Should be "cool" heading below

##### cool

Stuff

#### Tab 2

blop

[hadley]

It's probably because when you use a h1 in page, pkgdown automatically shifts it, and all other headings, down one level. I think that probably messes up something with the tabset code. But I think the fix is just not to use <h1> in pages :) (Because a page should only have a single <h1> and that's the page title).