To complete @jdb reply,
PANDOC is what is used behind the scene of Rmarkdown. You can do slides directly with PANDOC using a markdown file and converting to the correct supporting format
https://pandoc.org/MANUAL.html#producing-slide-shows-with-pandoc
rmarkdown can be used with md file directly without any R code chunk to run as he shows.
Example for a reveal js presention in a test-reveal.md file
---
title: "Untitled"
output: revealjs::revealjs_presentation
---
## R Markdown
This is an R Markdown presentation. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.
When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document.
## Slide with Bullets
- Bullet 1
- Bullet 2
- Bullet 3
## Slide with R Code and no Output
```r
summary(cars)
```
## Slide js code as example
```js
document.getElementById("'para')
```
To render to Html with
rmarkdown::render("test-reveal.md")
Hope it helps