Support for project references / composite projects

[ajafff]

Is there a need to support linting composite projects? I'd like to get some feedback whether that actually makes sense.
The alternative is manually starting the linter for each project.

[ajafff]

Apparently this makes sense if you have multiple projects and one tsconfig.json that references all of them. That way you can build and lint all projects at once and don't have repeated startup time.

Requirements for the implementation:

• when a tsconfig.json is referenced by multiple other projects it should only be linted once
• the order of the linted projects probably doesn't matter
• when files are specified the implementation only lints the projects that contain any of the specified files