Invalid yaml metadata if articles in subdirectories

[Hadley Wickham]

e.g. for bslib:

[main] > pkgdown::as_pkgdown(".")$vignettes
# A tibble: 15 × 6
   name                    file_in                            file_out   title description depth
   <fs::path>              <fs::path>                         <fs::path> <chr> <chr>       <int>
 1 any-project/index       vignettes/any-project/index.Rmd    …ndex.html Any … NA              2
 2 bs4-variables/index     vignettes/bs4-variables/index.Rmd  …ndex.html Boot… NA              2
 3 bs5-variables/index     vignettes/bs5-variables/index.Rmd  …ndex.html Boot… NA              2
 4 cards/index             vignettes/cards/index.Rmd          …ndex.html Cards NA              2
 5 column-layout/index     vignettes/column-layout/index.Rmd  …ndex.html Colu… NA              2
 6 custom-components/index …ettes/custom-components/index.Rmd …ndex.html Cust… NA              2
 7 dashboards/index        vignettes/dashboards/index.Rmd     …ndex.html Dash… NA              2
 8 examples/index          vignettes/examples/index.Rmd       …ndex.html Exam… NA              2
 9 filling/index           vignettes/filling/index.Rmd        …ndex.html Fill… NA              2
10 sidebars/index          vignettes/sidebars/index.Rmd       …ndex.html Side… NA              2
11 theming/index           vignettes/theming/index.Rmd        …ndex.html Them… NA              2
12 tooltips-popovers/index …ettes/tooltips-popovers/index.Rmd …ndex.html Tool… NA              2
13 utility-classes/index   …gnettes/utility-classes/index.Rmd …ndex.html Util… NA              2
14 value-boxes/index       vignettes/value-boxes/index.Rmd    …ndex.html Valu… NA              2
15 why-sass/index          vignettes/why-sass/index.Rmd       …ndex.html Why … NA              2

Which yields:

articles:
  index: any-project/index.html
  index: bs4-variables/index.html
  index: bs5-variables/index.html
  index: cards/index.html
  index: column-layout/index.html
  index: custom-components/index.html
  index: dashboards/index.html
  index: examples/index.html
  index: filling/index.html
  index: sidebars/index.html
  index: theming/index.html
  index: tooltips-popovers/index.html
  index: utility-classes/index.html
  index: value-boxes/index.html
  index: why-sass/index.html

Because article_index() strips the directory name.

Not sure what the right thing to do here is. Maybe just drop them from the index because there's no way to autolink to them anyway? (i.e. this really should just be a list of vignettes, not articles). But that's probably a bad idea if we ever do add auto-linking syntax. So maybe ok to just use the name unprocessed?