Add styling to kbd shortcode keyboard shortcuts in Revealjs presentations

[cderv]

kbd styling is among the .scss we need to make available to revealjs as it works for HTML with bootstrap.
Related on that topic to

• [Revealjs] Allow customisation of callouts similar as in HTML  #5038

And also related to other kbd works

• Monospace font for kbd tad/shortcode is not pretty #5879
• kbd shortcode has accessibility issues #5403

Discussed in #6009

^{Originally posted by c-zippel June 23, 2023}

Description

It'd be neat if keyboard shortcuts produced with the kbd shortcode in Reveal presentations were styled similarly to those in HTML documents, with a grey background and outline, rather than as normal slide text.

In HTML:

In Reveal:

Thank you for considering this feature request!

.qmd for the screenshots

---
format: 
  html: default
  revealjs: 
    output-file: revealjs.html
---

## Keyboard Shortcut

Here's a keyboard shortcut: {{< kbd Ctrl+S >}}