feature request - option to attach own headers and callbacks on ping request

[adeptofvoltron]

to make it easier lets start with some user story:

In my app I do check every 30 seconds if backend is online...using react-detect-offline. But also I do every 30 seconds check for number of user notifications.

So not to generate too many backend requests I would love to kill 2 birds with one stone

So maybe I can attach own headers (like auth token) and own callback to the request object you are creating.

waiting for your opinion