Ignore bad typings properties in package.json files

[amcasey]

Otherwise, the non-existent typings file becomes part of the project and a spurious non-existent-root-file error is reported.

This was reported by a customer using source-map.

This is pretty rare, but we could go above and beyond by trying to add the file extension ourselves.

[amcasey]

Note to self: if we keep module resolution, confirm I didn't just break all packages with a file extension.

Moot

[minestarks]

@amcasey - is there more work to do on this?

[zkat]

Closing in favor of #47164