UX Issue: Keys Not Labeled

Bug description

Here is an example of a webpage which is confusing to read. Once someone becomes more comfortable with Quarto, it's hard to tell if a command is specifically for _quarto.yml, specifically for index.qmd or about.qmd, a yaml (say in doc xxx.qmd), a subsection (in xxx.qmd), or _publish.yml.

• For example, I may want to set my figures in my HTML webpage xxx.qmd to centred. The linked website + image make it hard to know if these are commands to use in the ![]() or the yaml.

This is more of a stylistic choice for simplifying communication, but it is such a barrier to using Quarto that it kind of is a bug.

• For example, if the keys were even colour-coded rather than just purple, that might help users know which commands were for a yaml, for which doc type, or if they are feature-specific (in text only). Thanks so much!

System Info

• Mac OS
• R version 4.2.2 (2022-10-31)

Quarto Check
[✓] Checking versions of quarto binary dependencies...
Pandoc version 3.1.1: OK
Dart Sass version 1.55.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
Version: 1.3.326
Path: /Applications/quarto/bin

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

[✓] Checking Python 3 installation....OK
Version: 3.9.13 (Conda)
Path: /Applications/anaconda3/bin/python
Jupyter: 4.11.2
Kernels: python3, ir

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

[✓] Checking R installation...........OK
Version: 4.2.2
Path: /Library/Frameworks/R.framework/Resources
LibPaths:
- /Library/Frameworks/R.framework/Versions/4.2/Resources/library
knitr: 1.42
rmarkdown: 2.21

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

Checklist

• 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.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.
• Please provide the output of quarto check so we know which version of quarto and its dependencies you're running.