### Bug description

Following the ["Metadata Listings" section](https://quarto.org/docs/websites/website-listings-custom.html#metadata-listings) in the documentation, it is possible to include custom metadata in YAML, either in individual files or in front matter, and have that metadata show up in a custom listing template.

For instance, we can create a listing page:

**index.qmd**

````
---
title: "Testing"
template: custom.ejs
contents:
- name: First Item
  href: https://www.quarto.org
  custom-field: A **custom value**
- name: Second Item
  href: https://www.rstudio.org
  custom-field: A *second* custom value
---

Blah
````

…and a custom EJS template:

**custom.ejs**

````
```{=html}
<ul>
<% for (const item of items) { %>
  <li>
    <a href="<%- item.href %>"><%= item.name %></a><br/>
    <%= item['custom-field'] %>
  </li>
<% } %>
</ul>
```
````

…and it will render the custom field in an HTML list:

```
<ul>
        <li>
            <a href="https://www.quarto.org/">
                First Item
            </a><br>
            A **custom value**
        </li>
        <li>
            <a href="https://www.rstudio.org/">
                Second Item
            </a><br>
            A *second* custom value
        </li>
</ul>
```

However, any Markdown formatting in the custom field is *not* rendered—it renders the text as `A **custom value**` instead of `A <strong>custom value</strong>`

It could be helpful to have a helper function of sorts accessible by EJS files, like 

```
<%= parseMarkdown(item['custom-field']) %>
```

Rendering works as expected when raw HTML is used in the metadata. That is,

```
- name: First Item
  href: https://www.quarto.org
  custom-field: A <strong>custom value</strong>
```

… turns into 

```
<li>
    <a href="https://www.quarto.org/">
        First Item
    </a><br>
    A <strong>custom value</strong>
</li>
```

---

This is with Quarto 1.3.26 in RStudio 2022.07.2+576 (and also in VS Code) on macOS Monterey 12.6

### 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.
dragonstyle
2022-11-27T04:32:10Z
andrewheiss
enhancement
v1.4
open
Markdown in custom listing fields not rendered by EJS template
https://github.com/quarto-dev/quarto-cli/issues/3468