AWS::Config::RetentionConfiguration

It is not possible to set a retention configuration in AWS Config at the moment.
## 1. Title

#### AWS::Config::RetentionConfiguration

## 2. Scope of request
b) new resource type for an existing service is desired

#### AWS::Config::RetentionConfiguration

## 3. Expected behavior

During create and update, call https://docs.aws.amazon.com/config/latest/APIReference/API_PutRetentionConfiguration.html

During delete, call https://docs.aws.amazon.com/config/latest/APIReference/API_DeleteRetentionConfiguration.html

## 4. Suggest specific test cases

## 5. Helpful Links to speed up research and evaluation

https://docs.aws.amazon.com/config/latest/APIReference/API_PutRetentionConfiguration.html
https://docs.aws.amazon.com/config/latest/APIReference/API_DeleteRetentionConfiguration.html

## 6. Category (required)

Use the categories as displayed in the AWS Management Console (simplified):

5. Management (CloudTrail, Config...)