stet runs on a site that's only HTML files: marked elements, one file for the words, and a check that catches hand edits.
A site with no framework and no build step can use stet. stet init sets it
up, stet register marks each element it manages with a data-stet
attribute, and stet pull rewrites every marked element from
content/defaults.json. stet check names any marked text edited by hand,
page titles and descriptions bind to their keys, and stet eject removes
every mark while the text stays.