feat(apigateway): Adds construct which allow configuring ratelimiting at api key level

Incorporates changes from code review.

Author: Vaibhav Walia

packages/@aws-cdk/aws-apigateway/lib/rate-limited-api-key.ts

@@ -38,7 +38,7 @@ export class RateLimitedApiKey extends Resource implements IApiKey {
       physicalName: props.apiKeyName,
     });
 
-const resource = new ApiKey(this, 'Resource', props);
+    const resource = new ApiKey(this, 'Resource', props);
 
     if (props.apiStages || props.quota || props.throttle) {
       new UsagePlan(this, 'UsagePlanResource', {