Add support for APIGateway event with custom authorizer

[krishnagopinath]

Some AWS lambdas are invoked via custom authorizers and they have the type APIGatewayProxyWithLambdaAuthorizerEvent<TAuthorizerContext>. With the current 'aws:apiGateway' eventType, setting up something like this:

const event = createEvent('aws:apiGateway', {
  body: JSON.stringify({ message: 'this is a message' }),
  requestContext: {
	authorizer: {
	  user: JSON.stringify({ id: 12345, name: 'Satoshi Nakamoto', roleId: 1 }),
	},
  },
});

... results in this TypeScript error:

Type '{ authorizer: { user: string; }; }' is missing the following properties from type 'APIGatewayEventRequestContextWithAuthorizer<APIGatewayEventDefaultAuthorizerContext>': accountId, apiId, protocol, httpMethod, and 7 more.

I wonder if it would make sense to either

1. Apply a DeepPartial on body to allow for nested requestContext.
2. Create a new eventType called 'aws:apiGatewayWithCustomAuthorizer'.

I like Option 2 better because of it being hyper clear about what it is doing.