Testing utils

[nick-stebbings]

Adding a package for testing utilities that exports:

• A stores object that provides API for easily mocking a sensemaker or matrix store (with possible nested profile, sensemaker stores) with a given set of sensemaker primitives
• A factories object that generates realistic mock objects for use in testing or Storybook.

Currently you can look at the API by examining the tests in the stores/__tests__ folder.
Currently released as a package @neighbourhoods/testing-utils so that I could check importing from the launcher.

• Add documentation for the above APIs
• Complete the Sensemaker, nested sensemaker store features by moving the rest of the code from the nh-launcher
• Decide if this even should live in this repo!

[pospi]

looks useful, nice start