We will have to do this regularly in order to upload it to Crowdin (or Weblate
or whatever translation system we are going to use).
Unlike the non-English JSON files, the en.json file is not committed to the git
repo.
We write a hacky, one-off script to do that. We need this script only once, so
we don't bother polishing it much. We'll re-purpose it later in the branch to
convert the English translation set to JSON; that is an operation that we need
to do regularly in the future.