### Bug description

Hi. As always, thank you, thank you, thank you for this awesome software. 

As the title states, for revealjs documents, fontawesome icons used in section headers do not appear in the presentation outline. Unicode/HTML does, though.

````md
---
title: "Test Prez"
format: revealjs
---

## Slide 1 📋 

## Slide 2 {{< fa brands r-project >}}

## Slide 3 &#x1F3AF;
````

Output:
<img width="338" alt="image" src="https://user-images.githubusercontent.com/53311626/212113357-6aae228e-65b4-4c6e-8e52-62ac7bde7ea1.png">

```
> sessioninfo::session_info()
─ Session info ──────────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.2.1 (2022-06-23 ucrt)
 os       Windows 10 x64 (build 22621)
 system   x86_64, mingw32
 ui       RStudio
 language (EN)
 collate  English_United States.utf8
 ctype    English_United States.utf8
 tz       America/Denver
 date     2023-01-12
 rstudio  2022.12.0+353 Elsbeth Geranium (desktop)
 pandoc   NA
```
Not sure why it's not showing my pandoc version, but here's this:
```
> rmarkdown::find_pandoc()
$version
[1] ‘2.19.2’

$dir
[1] "C:/Program Files/RStudio/resources/app/bin/quarto/bin/tools"
```

Thanks!

### Checklist

- [X] Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
- [X] Please [format your issue](https://quarto.org/bug-reports.html#formatting-make-githubs-markdown-work-for-us) so it is easier for us to read the bug report.
- [X] Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
- [X] Please document the operating system you're running. If on Linux, please provide the specific distribution.
2023-01-12T15:54:50Z
kbvernon
bug
closed
revealjs - fontawesome icon in section header does not appear in presentation outline
https://github.com/quarto-dev/quarto-cli/issues/3950