Four right-to-left languages at /ar/, /he/, /fa/ and /ur/ — thirteen in all.
The layout no longer has a left and a right, it has a start and an end: the
margins, insets and corners are CSS logical properties now, so they follow
dir on <html>. Directional glyphs flip; keys, safety codes and session
descriptors are pinned left-to-right so bidi cannot reorder what two people
compare against each other's screens.
Also fixed: the Service Worker was registered as './sw.js', which 404s from
every locale subdirectory, so twelve of the thirteen pages had no worker at
all. And the bundler ran before the dictionaries were generated, so a newly
added language could reach the page ahead of the app that renders it.
