Improved options run time configuration

[tomgp]

We could use cosmiconfig to manage run time configuration in different places.

At the moment the options are either a .datasupplyrc file or another file supplied as a command line argument
supply --config CONFIG.json cosmiconfig handles config in different places and applies them with a conventional, predictable precedence order this would make it easier to e.g. have a dynamic config via .js file for different environments (CI etc.)

[github-actions]

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