tsconfig.json: extends path allows Node resolution

[sirreal]

Add a phrase indicating that the extends option may use Node.js tyle module resolution.

This was surprising to me based on the current language in the handbook, but observed behavior and source seem to indicate that Node.js module resolution is allowed:

https://github.com/microsoft/TypeScript/blob/7c14aff09383f3814d7aae1406b5b2707b72b479/src/compiler/commandLineParser.ts#L2402-L2406

[orta]

👍 cool, thanks