Add Application.prototype.handleError

[javan]

Supply your own error handler function to override the default console.error. Useful for sending errors to a tracking service like Sentry.

const application = Application.start()

application.handleError = (error, message, detail) => {
  console.warn(message, detail)
  Raven.captureException(error)
}

[rwojsznis]

Welp, that caught me by surprise (obviously in production 😅 )

I would never-ever except such library to swallow errors for me - maybe I ask why throw is not the default here? (so if you have sentry it will be reported properly via window.onerror by default)

And ofc thanks for this PR @javan ! ❤️

[sstephenson]

@emq Could you open a new issue so your comment doesn’t get lost in the stream? Thank you!