PackageResolver
Where a bare package import in a scratch file resolves when tcm provides the package: the cache's directory for the version chosen for that file. Undefined leaves the import to ordinary resolution (the project's own node_modules).
export type PackageResolver = ((name: string, containingFile: string) => { specifier: string; from: string } | undefined) & { /** identifies the mapping: a compiler keeps resolutions per key, so a changed mapping resolves afresh */ key?: string; };