message: refine the STYLE_GUIDE content
diff: ## Development
  The document contains the necessary information for setting up the development environement
  -and building the `tensorflow-io` package from source on various platforms.
  +and building the `tensorflow-io` package from source on various platforms. Once the setup is completed please refer to the [STYLE_GUIDE](https://github.com/tensorflow/io/blob/master/STYLE_GUIDE.md) for guidelines on adding new ops.
  ### IDE Setup
  