Markdown headers shouldn't be exported as workspace symbols in R packages

[lionel-]

Once activated, the Quarto extension currently scans all md files and exports section headers to workspace symbols. While great generally, this can get in the way of the dev workflow in R packages.

R packages may include a variety of md files:

• Snapshot files: https://github.com/tidyverse/ellmer/tree/main/tests/testthat/_snaps
• Documentation: https://github.com/r-lib/rlang/tree/main/man/rmd

This causes Quarto to flood workspace symbols with headers that are mostly irrelevant for package development:

Screen.Recording.2025-07-03.at.15.25.47.mov

Reported by @hadley and I also have the same issue e.g. when I'm working on rlang.