JSON files are now sorted by key with `prettier`, using the plugin
`prettier-plugin-sort-json`. This does not affect `package.json`
because `prettier` uses a special parser for that file, as it has
a more restrictive format than JSON.
Instead of using `eslint-plugin-json` for linting JSON files,
`prettier` is now used. `prettier` is capable of detecting and
correcting more problems than `eslint-plugin-json` can, such as
indentation.
All JSON files have been run through `prettier`. The changes are all
superficial.