General Problem
---------------

Given a package that provides R Markdown templates, **how does one get a list of all valid templates** that could be given to the `rmarkdown::draft` function? That is, for

```r
rmarkdown::draft("my_rmd.Rmd", template_name, some_pkg)

```

where we know `some_pkg`, how can one programmatically obtain the valid values for `template_name`?

Example Package: reprex
-----------------------

As a concrete example of a template provider, let's use the **reprex** package. From the RStudio GUI, I know **reprex** provides two templates. How can one get the list of `template_names` for the **reprex** package?

What I've Looked Through
------------------------

Skimming through the `rmarkdown::` methods, I don't see any such functionality. Searching around, I've only found examples for how to write and use templates, but all eventually resort to showing how to load the template via the RStudio GUI dialog. The documentation of the `rmarkdown::draft` only describes where the templates are stored, but doesn't provide a programmatic example for listing them.