@Nonnull
	default Path getFile() {
		throw new IllegalStateException("Getting file from stream not implemented");
	}
Returns a file representation for this resource reference. If an original
resource was provided, this method will return a resolved file representation
of that resource. Depending on the resource reference, the process of
resolving might have been done when the reference was created, or it might be
done when calling this method. In which case some kind of RuntimeException
might be thrown if the resolving process fails.

@return A file reference
src/main/java/dev/jbang/source/ResourceRef.java