Directory the generated import map will be read from, as a path or file:// URL.

Manifest targets are written relative to root, but Deno resolves an import map's relative targets from the location of the map file. Each relative target is rewritten to be relative to this directory instead, so it still points at the right file once the map moves. writeImportMap and the CLI set this automatically to the output file's directory; set it yourself only when placing an in-memory map somewhere other than root. Defaults to root.