default void monitorFile(String name, Path path, LongSupplier sizeProvider) {
    if (path != null) {
      monitoredFiles().put(name, new MonitoredFile(path, sizeProvider));
    }
  }
Adds a stat that will track the size of a file or directory located at {@code path}.
planetiler-core/src/main/java/com/onthegomap/planetiler/stats/Stats.java