revealjs: specifying a font-face using local files requires annoying use of ../

Bug description

If you want to use a font from a file you need to use a lot of ../ to get to the right area. If both your styles.scss file and the font files are in the same directory as index.qmd you need to prefix the file names with ../../../../../ since the compiled scss ends up in index_files/libs/revealjs/dist/theme/quarto.css but the fonts stay where they are.

Steps to reproduce

Repo: https://github.com/EmilHvitfeldt/quarto-custom-font-revealjs-reprex

Page: https://emilhvitfeldt.github.io/quarto-custom-font-revealjs-reprex/

Expected behavior

It would be lovely if the @font-face could be specified with the following code

@font-face {
    font-family: 'FiraCode';
    src: url('FiraCode-Regular.woff2') format('woff2'),
         url('FiraCode-Regular.woff') format('woff');
}

Actual behavior

Where as now, you have to specify to a variant of

@font-face {
    font-family: 'FiraCode';
    src: url('../../../../../FiraCode-Regular.woff2') format('woff2'),
         url('../../../../../FiraCode-Regular.woff') format('woff');
}

Your environment

• IDE: Version 2023.05.0-daily+206 (2023.05.0-daily+206)
• OS: macOS Monterey version 12.6

Quarto check output

[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.2: OK
      Dart Sass version 1.55.0: OK
      Deno version 1.33.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.4.92
      Path: /Applications/quarto/bin

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.9.7 (Conda)
      Path: /Users/emilhvitfeldt/miniforge3/bin/python
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with conda install jupyter

[✓] Checking R installation...........OK
      Version: 4.2.1
      Path: /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources
      LibPaths:
        - /Users/emilhvitfeldt/Library/R/arm64/4.2/library
        - /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/library
      knitr: 1.43
      rmarkdown: 2.21

[✓] Checking Knitr engine render......OK

Start by reproducing the issue with the linked quarto-custom-font-revealjs-reprex repository, using its index.qmd, styles.scss, and local font files. Inspect how styles.scss becomes index_files/libs/revealjs/dist/theme/quarto.css and how asset paths are handled. Done means local @font-face URLs work without repeated ../ prefixes.