New Pattern: appsync-dynamodb

Similar to as we have API gateway -> DynamoDB or Api gateway -> lambda -> DynamoDB, we should also have a pattern that covers GraphQL resolvers to DynamoDB (AppSync to DynamoDB).

### Use Case

Most of the constructs for APIs that we have today are targeted towards REST based services but none towards GraphQL based APIs. AppSync and GraphQL being the next generation of API platform to support, construct with AppSync with DynamoDB will help customers to build their applications faster.

### Proposed Solution

TBD, but at a high level
1. construct props to define the resolvers
2. define and configure DynamoDB
3. configure permissions required for AppSync authentication model
4. role permissions to allow AppSync to connect with DynamoDB

### Other

* [X] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

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This is a :rocket: Feature Request

Start by reviewing the existing API Gateway-to-DynamoDB and API Gateway-to-Lambda-to-DynamoDB patterns for the project's conventions. Define the resolver props, DynamoDB configuration, AppSync authentication permissions, and AppSync-to-DynamoDB role permissions described in the issue; the issue provides no file or test entry point, and the proposed solution remains TBD.

Written by the indexing model from the issue text.