Option to disable sending events and only log them

[TriPSs]

During development it would be quite handy if we could disable the actual sending of events and only log what would have been send.

This will make implementing PostHog events easier and wont pollute the dashboard with test data.

[benjackwhite]

This is cool idea. How would you expect the SDK config to look like for this?

[TriPSs]

The posthog-node SDK has a disabled option, maybe we can add that to? If debug is then enabled it will then log (like now) the events to the console.