docs: public void spacingFile(File inputFile, File outputFile) throws IOException {
          // TODO: support charset
  
          FileReader fr = new FileReader(inputFile);
          BufferedReader br = new BufferedReader(fr);
  
          outputFile.getParentFile().mkdirs();
          FileWriter fw = new FileWriter(outputFile, false);
          BufferedWriter bw = new BufferedWriter(fw);
  
          try {
              String line = br.readLine(); // readLine() do not contain newline char
  
              while (line != null) {
                  line = spacingText(line);
  
                  // TODO: keep file's raw newline char from difference OS platform
                  bw.write(line);
                  bw.newLine();
  
                  line = br.readLine();
              }
          }
          finally {
              br.close();
  
              // 避免 writer 沒有實際操作就 close()，產生一個空檔案
              if (bw != null) {
                  bw.close();
              }
          }
      }