Set NODE_ENV at run time or build time to switch the app between dev and
production modes.
At build time, the current NODE_ENV will be included in the packaged
app's package.json file. At runtime we read NODE_ENV from package.json,
but also allow the local environment variable to override. A query
string parsed by a preload script exposes the value to the renderer,
which then determines whether we use the staging or production server.
Additionally, different environments have different user data
directories.
// FREEBIE
