Data generation doesn't work in the decorator from @nova/react-test-utils when used with client extensions

[sjwilczynski]

Here is repro https://github.com/jakobkhansen/nova-facade/tree/user/jakobhansen/clientextension_repro.

The current workaround is to change generateFunction to use Relay's mock payload generator but long term we want to rely on graphitations one fully

[sjwilczynski]

Added proper readme entry and example of a workaround in #127