message: add notebook formatting instruction in README
diff: @@ -176,6 +176,8 @@ Lint fix an individual python file with black and pyupgrade using:
  $ bazel run //tools/lint:lint -- black pyupgrade -- tensorflow_io/core/python/ops/version_ops.py
  ```
  +### Notebooks/Tutorials
  +If you are updating or creating a notebook, please refer to the tutorials and instructions mentioned [here](https://github.com/tensorflow/io/tree/master/docs/tutorials).
  ### Python
  