This makes no difference to how the site is built under Dactyl (other
than where the "Edit Page" links go) but changes the URLs that will
be used for the pages after the migration to Redocly.
In addition to renaming index pages to index.md, I updated the style
guide to reflect the updated conventions, and moved a couple files that
were not in the correct folders for their place in the nav hierarchy.
Part of IA and Redocly migration work. Create simple .md files to
represent the automatic index pages that previously only existed in
the dactyl-config.yml file. (The code used to do this is also part
of the commit but is, hopefully, no longer needed.)
The new folder will be compatible with both Dactyl and Redocly when it
comes to loading the Japanese translation for a given page.
Snippets are not moved for now because importing them would require
more complex changes to the actual Markdown pages, and wouldn't be
cross-compatible anyway (Redocly uses slightly different 'partial'
rather than 'include' syntax.)
