The filenames draft_book() would write, without the .qmd extension.
Useful for cross-referencing chapters or checking a _quarto.yml against
the schedule.
Examples
schedule <- system.file("extdata", "schedule.md", package = "rithmatist")
chapter_slugs(schedule)
#> [1] "project-organisation" "code-style-and-readability"
#> [3] "writing-readable-code" "writing-functions"
#> [5] "writing-a-reprex-getting-unstuck" "putting-it-all-together"