code: public static List<File> getFilesByExtension(File path, String extension)
      {
          Check.notNull(path);
          Check.notNull(extension);
  
          final List<File> filesList = new ArrayList<>(1);
          getFilesByExtensionRecursive(filesList, path, extension);
          return filesList;
      }
docs: Get all files existing in the path considering the extension.
  
  @param path The path to check (must not be <code>null</code>).
  @param extension The extension without dot; eg: png (must not be <code>null</code>).
  @return The files list.
  @throws LionEngineException If invalid arguments.