Static mock docs updated to reflect usage and include a complete working example

[DawMatt]

The static mock documentation did not reflect the feature's expectations and behaviour explained in issue #153 .

The documentation has been updated to:

• include a valid command line as the first example of how to use the feature (i.e. added -u parameter)
• fix an invalid example JSON document (get-test-mock.json), which had a trailing comma where it shouldn't have been.
• extended the example to include the wiretap and curl commands to test the example, added the expected response JSON document, and adjusted the directory structure to be relative to whereever the user is running the command.

Hopefully this is enough of a change that users can have a successful first test of the feature purely by following the steps laid out in the example.

CC @akash4393

[akash4393]

This is great! Thank you so much @DawMatt :)

[DawMatt]

This is great! Thank you so much @DawMatt :)

Thanks @akash4393 for adding the static mock feature!

I'm hoping to get some of our more data-oriented/less technical people using this + Postman to help mock up APIs and responses earlier during projects. OpenAPI would be too much for them but I think we can find a way to make this approachable for them.