Improve AWS::ResilienceHub::App capability

### Name of the resource

Other

### Resource name

AWS::ResilienceHub::App

### Description

Improve the experience of creating a resiliency hub application using CloudFormation. The CloudFormation resource should automatically generate the AppTemplateBody property based on CFN stacks provided. This can be difficult to manually do if there is many resources that can be included. In the management console this is done for you and creating an application is a way better user experience.

### Other Details

The CloudFormation documentation is also not complete missing details and examples.

No repository files, tests, or entry points are named. Start by reviewing the AWS::ResilienceHub::App resource behavior and the management-console flow for generating AppTemplateBody from supplied CloudFormation stacks, then inspect the resource documentation. Done means the resource can generate the property from provided stacks and the documentation includes the missing details and examples.

Written by the indexing model from the issue text.