Doug dynamodb examples (#296)

* Added DynamoDB PutItem code example

* Added DynamoDB CreateTable, PutItem, and DeleteItem code examples

* Added DynamoDB ListTables, ListItems, and DeleteTable code examples

* Updated DynamoDB CreateTable code example

* Updated DynamoDB code examples after running clippy

* Updated DynamoDB code examples with latest changes

* Updated DynamoDB code examples

Co-authored-by: Russell Cohen <rcoh@amazon.com>