Allow custom configuration options?

[zkamvar]

At the moment, it's not possible to add custom configuration options site-wide, which hampers lessons like HPC intro. They have a lot of customization in their config files and I want to make sure that their transition is relatively painless.

Luckily, pandoc has support for custom metadata configuration on top of lua filters: https://pandoc.org/MANUAL.html#default-files

[zkamvar]

This could be done using R Markdown syntax, but it's less than ideal.

At the moment, {sandpaper} does not support parameterised reports, but it shouldn't be that difficult to implement (e.g. allowing folks to add an extra params.yaml to specify parameters).

Take, for example this section on modules

### Listing Available Modules


To see available software modules, use `module avail`:


```
{{ site.remote.prompt }} module avail
```
{: .language-bash}


{% include {{ site.snippets }}/modules/available-modules.snip %}

If we were to translate this to use child documents and params, it might look something like this:

### Listing Available Modules


To see available software modules, use `module avail`:


```{r, results='asis'}
sprintf("```\n%s module avail```", params$remote.prompt)
```


```{r child=file.path(params$snippets, "modules/available-modules.snip")}
```

When we support quarto, it might be easier because we could use this syntax (I think):

### Listing Available Modules


To see available software modules, use `module avail`:


```
{{< var remote.prompt >}} module avail
```


{{< include {{< var snippets >}}/modules/available-modules.snip >}}

Of course, one thing I could do is also insert lua filters that will achieve the same goal as quarto and use the same syntax until we can support quarto.