Serialize and send page error instead of ErrorEvent

[ghost1542]

window.addEventListener('error', is sending back ErrorEvent objects instead of Error objects.

Since the following code snippet only accepts instances of Error, the object is returned as is, and not much ends up serialized and sent back by preload.js, just a bunch of { isTrusted: true }.

/**
 * Make errors serializeable
 */

function error(err) {
  if (!(err instanceof Error)) return err <--------------------
  return {
    code: err.code,
    message: err.message,
    details: err.detail,
    stack: err.stack || ''
  }
}

Fixing preload.js to serialize and send the Error object instead appears to match the initial intent.