docs: add links to terraform backend and app runner stacks

Author: tiagoboeing

README.md

@@ -8,6 +8,8 @@ Infrastructure as Code (IaC) stacks for Amazon Web Services (AWS).
 
 ![Terraform](https://img.shields.io/badge/terraform-%235835CC.svg?style=for-the-badge&logo=terraform&logoColor=white)
 
+- [Terraform Backend with S3 and DynamoDB (Remote State + State Locking)](./terraform-backend)
+- [App Runner with ECR, CloudFront, ACM and Route53](./app-runner)
 - [Cognito User Pool with Identity Providers (social logins)](./cognito-user-pool)
 - [CDN on custom domain with CloudFront, S3, Route53 and Certificate Manager](./cloudfront-cdn)
 - [ECS Cluster with VPC, NAT Gateway, Internet Gateway and custom domain](./ecs-cluster-vpc-nat)