`format-links` should support `target` attributes, and in general same attributes option as `other-links`

Discussed in https://github.com/quarto-dev/quarto-cli/discussions/10729

^{Originally posted by aghaynes September 6, 2024}

Description

In a quarto website, I'd like to provide PDF versions of the various pages, which works great by setting

format:
  html: default
  pdf: default

But I would like the PDF to open in a new window (or even appear as a download), which i would normally do with target="_blank". According to the quarto website, it's possible to use format-links to customise the links, including any of the options from [https://quarto.org/docs/output-formats/html-basics.html#code-links-and-other-links](the code links section).

Unfortunately, I've been unable to get the target option to work. I've tried all four variants that come to mind ("blank", "_blank", blank and _blank), but none seem to work for the PDF, nor generic links. I also don't see the target attribute in the generated HTML code...

Am I missing something, or is it ignoring the additional attributes? I don't see the target attribute in the generated HTML code...

The target does work with other-links though via target: _blank...

---
title: "x"
format: 
  html: default
  typst: default
format-links:
  - html
  - format: typst
    text: PDF
    icon: file-pdf
    target: _blank
  - text: Other Link
    href: https://quarto.org/
    icon: hand-thumbs-down
    target: _blank
other-links:
  - text: Another Link
    href: https://quarto.org/
    icon: hand-thumbs-up
    target: _blank
---

This is a Quarto website.

To learn more about Quarto websites visit <https://quarto.org/docs/websites>.

```{r}
1 + 1
```

Thanks for any suggestions!

Reproduce the issue with the provided Quarto document, using format-links and other-links with target: _blank. Compare the generated HTML for both link types; done means format-links preserves the target attribute for PDF and generic links, with tests or output confirming the behavior.