Tooling support for TypeScript project references

[mjbvz]

Tracks general tooling support for TypeScript 3.0's new project references feature: microsoft/TypeScript#3469 (comment)

Ideas

• Allow click on tsconfig references paths #54215 Clickable links for project reference paths
• Error reporting for invalid project references (blocked on configFileDiag not returning errors for missing project reference path TypeScript#25741)
• Json schema update - Add references to tsconfig.json SchemaStore/schemastore#498

[mjbvz]

Closing this for july. Will follow up in the error reporting issue upstream