Create a GraphQL query for contributed projects

Background

For &13066 (closed) we want a way to show projects that users have contributed to in the Contributed tab. We already have GET /users/:user_id/contributed_projects but for API parity we should try make this data available via GraphQL as well. See discussion in #446241 (closed)

Implementation guide

Add a new Query.user.contributedProjects GraphQL query by adding a new field contributed_projects similar to starred_projects in UserInterface and use the ContributedProjectsFinder to get the contributed projects. Add a sort arg to the resolver and make latest_activity_desc its default value.