[FEAT] Add CI to CONTRIBUTING.md

[RossKen]

Is your proposal related to a problem?

Building ontop of #1394 - the CI pipelines are something that are not really documented anywhere and can trip up developers

Describe the solution you'd like

Add a section to the contributing guide on what CI / Actions are in place, and what any contributors can expect when dealing with them. E.g. what fails when running on a fork

Describe alternatives you've considered

Additional context

[RossKen]

This should also add instructions on the dev flag for running CI as added in #1433