[Test Runner] add test-scripts

[psimk]

@pota/test-scripts

This requires additional research before we can make a sound plan on what we want test-scripts to be.

• what test runner package should we use?
• is this purely for unit testing or also e2e?
  • if only unit testing, should this then be @pota/unit-test-scripts ?
• what things should it support out of the box? (there will be test-scripts packages for each framework)
  • code coverage?
  • running in watch mode?

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See #39 for context