Check that the app starts while offline

[simonw]

I just realized that hitting the plugin directory API on startup may cause the app not to work offline. Provided the dependencies are installed it should always work without an internet connection.

[simonw]

It does not: it hangs on the loading screen and the console log shows this:

{
  message: 'httpx.ConnectError: [Errno 8] nodename nor servname provided, or not known',
  type: 'stderr',
  ts: 2021-09-13T18:24:53.484Z
}