Add support for environment variables at project level

It would be very helpful to be able to specify environment variables on a project level as well.

We are a company with multiple big independent projects. We put company specific variables (e.g. credentials to artifact repository) at team level and any artifact specific variable at repository level. However, since all artifacts in a project should be deployed to the same environment would we like to put variables such as development environment, test environment etc. at project level. Putting them in pipeline configuration or at repository level would be too cumbersome and to put it at team level would clutter those settings (i.e. for each project adding PROJECT_DEVELOPMENT_ENVIRONMENT, test etc. to team settings).

I think this is a valid use case for the requested feature and hope to see it in the future!