message: doc: update README for using a simple shell command to modify the config file
  [skip ci]
diff: @@ -156,6 +156,12 @@ Update `data_dir` configuration in config file to a different directory.
  "data_dir": "node2"
  ```
  +or using a simple shell command to modify the config file:
  +
  +```shell
  +ex -sc '%s/"data_dir": "default"/"data_dir": "node2"/|x' nodes/node2.json
  +```
  +
  Then start the new node using the new config file
  ```shell
  