static ResourceRef forLazyFileResource(@Nonnull String resource, @Nonnull Function<String, Path> obtainer) {
		return new FileResourceResolver.FileResourceRef(resource, obtainer);
	}
Creates a new {@code ResourceRef} instance for a resolved resource. It takes
the original resource string, which can be things like file paths, urls,
classpath references, etc and associates it with the given file reference.

@param resource the original resource as a string
@param obtainer a function that obtains a file for the given resource string
@return a {@code ResourceRef} instance representing the specified resolved
        resource
src/main/java/dev/jbang/source/ResourceRef.java