Upkeep for glitter (2023)

[maelle]

• [x] usethis::use_tidy_description()
• [x] usethis::use_package_doc() Consider letting usethis manage your @importFrom directives here. usethis::use_import_from() is handy for this.
• [x] Align the names of R/ files and test/ files for workflow happiness. The docs for usethis::use_r() include a helpful script. usethis::rename_files() may be be useful.
• [x] usethis::use_code_of_conduct()
• [x] Add alt-text to pictures, plots, etc; see https://posit.co/blog/knitr-fig-alt/ for examples

Set up or update GitHub Actions. \ Updating workflows to the latest version will often fix troublesome actions:

• [x] usethis::use_github_action('check-standard')
• [x] usethis::use_github_action('pkgdown')
• [x] usethis::use_github_action('test-coverage')

^{Created on 2023-05-18 with usethis::use_upkeep_issue(), using usethis v2.1.6.9000}