@aws-appsync/utils incomplete type DynamoDBTransactGetItemsRequest

According to the [docs](https://docs.aws.amazon.com/appsync/latest/devguide/js-aws-appsync-resolver-reference-dynamodb-transact-get-items.html), `TransactGetItems` supports an optional `projection` on each element of the `transactItems` array. However, the optional `projection` attribute is missing from the `DynamoDBTransactGetItemsRequest` type.

Current (incomplete) type:

```ts
export type DynamoDBTransactGetItemsRequest = {
operation: 'TransactGetItems';
transactItems: {
table: string;
key: Key;
}[];
};
```

Expected type:

```ts
export type DynamoDBTransactGetItemsRequest = {
operation: 'TransactGetItems';
transactItems: {
table: string;
key: Key;
projection?: DynamoDBProjectionExpression;
}[];
};
```

My installed version: `"@aws-appsync/utils": "^1.12.0",`

Locate the @aws-appsync/utils definition of DynamoDBTransactGetItemsRequest and compare it with the AWS AppSync TransactGetItems documentation linked in the issue. Update the transactItems element type so projection is optional and uses DynamoDBProjectionExpression; done means the documented request shape is accepted by the type.

Written by the indexing model from the issue text.