feat: add CI workflow

[YOU54F]

Add a CI workflow that will

• Pull down a sample OpenAPI document
• Lint with Spectral
• Mock with Prism
• Test Mock with SoapUI
• Generate a consumer project with Swagger-Code-Generators
  • Project utilises a modified template to generate Pact consumer contract test
• Runs the consumer project to generate the Pact contracts
• Validates Pact contract against OpenAPI with @pactflow/swagger-mock-validator
• Retrieves a sample provider codebase, developed outside of the OpenAPI document (may suffer from provider drift)
  • Functionally test provider with SoapUI, leverage test suite previously pointed at Prism mock
  • Runs Pact provider verification tests which replay the consumers interactions, against our running provider

[frankkilcommins]

LGTM - will look to change the SHUB/APIHub one to do something similar and leverage the SHUB CLI.