chore:Documentation setup

Documentation: short of being able to publish this as [official AWS CDK constructs](https://docs.aws.amazon.com/cdk/api/v2/docs) (https://docs.aws.amazon.com/cdk/api/v2/docs) we can start documenting this project along with trp, and textractor projects using [readthedocs.io](http://readthedocs.io/) (http://readthedocs.io/) (just like how SageMaker does). We can have a docs/ folder in our repo with .rst files and set it up with our documentation, which could be more detailed than CDK HUB picking up the documentation from the comments in the constructs code (for CDK Constructs).