add changelog

# Changelog

## 1.3.2

### Features

- Lifted the requirement of the compulsory `'image'`-keyword target in each data sample.

  You can now use any valid keywords for your `image`-type targets 

- Added an example of using `Bio-Volumentations` with automatic augmentation strategies

  (`AutoAugment` and `RandAugment`)

### Changes

- Refactored the code

- Switched to using numpy random and vectorised operations to increase performance

- Improved code comments and warning messages

- Added more unit-tests (invalid input samples or parameters, keyword options, 

  vectorised implementation)