docs: void handleAdd() {
          BoofSwingUtil.checkGuiThread();
          java.util.List<File> paths = browser.getSelectedFiles();
  
          for (int i = 0; i < paths.size(); i++) {
              File f = paths.get(i);
  
              // if it's a directory add all the files in the directory
              if( f.isDirectory() ) {
                  java.util.List<String> files = UtilIO.listAll(f.getPath());
                  Collections.sort(files);
                  for (int j = 0; j < files.size(); j++) {
                      File p = new File(files.get(j));
                      // Note: Can't use mimetype to determine if it's an image or not since it isn't 100% reliable
                      if( p.isFile() ) {
                          selected.addPath(p);
                      }
                  }
              } else {
                  selected.addPath(f);
              }
          }
      }