With an increased amount of complexity in the frontend of the GUI
client, it pays off to initialise the Sentry React SDK to catch any
errors that might occur. In particular, any failing commands that we
issue to the backend will be caught that way as those rejected
`Promise`s will surface as uncaught exceptions.
Similar to the backend, Sentry in the frontend is only initialised for
known environments, i.e. our production and staging deployments of
Firezone. For on-premise installations, Sentry is disabled.
Related: #6138
