text: Title: Example code for speech to text using tensor2tensor
  Body: ### Description
  Hi, 
     Can you please share an example code to convert speech to text using Tensor2Tensor (maybe with transformer) mode?
  This will help a lot. 
  
  Thanks
  Nagaraju
  ...
  
  ### Environment information
  Python 3.7.7
  tensor2tensor 1.15.7
  ```
  OS: <Windows 10 (64 bit)>
  
  $ pip freeze | grep tensor
  # your output here
  
  $ python -V
  # your output here
  ```
  
  ### For bugs: reproduction and error logs
  
  ```
  # Steps to reproduce:
  ...
  ```
  
  ```
  # Error logs:
  ...
  ```
  