Hi,

the function `markdownToHTML`

in the package `markdown`

(current CRAN version 0.8) does not seem to correctly convert mathjax syntax on rstudio.cloud, but it works on my local windows notebook.

Here is a simple example:

```
library(markdown)
res = markdownToHTML(text = "MATH HERE: $x^2$", fragment.only=TRUE)
cat(res)
```

On my windows notebook, I get the correct mathjax compatible output:

```
<p>MATH HERE \(x^2\)</p>
```

Yet, running the same code on rstudio cloud yields the wrong HTML

```
<p>MATH HERE: $x<sup>2$</sup></p>
```

that Mathjax cannot handle. Interestingly, "mathjax" is set as default option on both my local notebook and rstudio.cloud:

```
# "mathjax" option is set in both environments
markdownHTMLOptions()
> markdownHTMLOptions()
[1] "skip_html" "skip_style" "skip_images" "skip_links" "safelink"
[6] "toc" "escape" "fragment_only" "hard_wrap" "use_xhtml"
[11] "smartypants" "base64_images" "mathjax" "highlight_code"
```

Also a possible workaround to directly write the markdown code in native mathjax format, like `\(x^2\)`

instead of `$x^2$`

does not work. While the RMarkdown package may work, it is much slower than `markdown::markdownToHTML`

and not well suited for my application.

To replicate the problem, you can also run the code in the file `mathjax_test.R`

in the following public cloud project: https://rstudio.cloud/project/46324