[Resource Type] - [Coverage] - AWS::GlobalAccelerator

### Name of the resource

Other

### Resource name

AWS::GlobalAccelerator

### Description

CloudFormation does not currently support Custom Routing for AWS Global Accelerator, which means users have to rely on AWS CLI or SDKs instead of managing these resources through infrastructure as code.

CloudFormation is missing key resources for Custom Routing, such as:

- CustomRoutingAccelerator ([Create API](https://docs.aws.amazon.com/global-accelerator/latest/api/API_CreateCustomRoutingAccelerator.html))
- AllowCustomRoutingTraffic ([API](https://docs.aws.amazon.com/global-accelerator/latest/api/API_AllowCustomRoutingTraffic.html))

Without CloudFormation support, users must manually configure Custom Routing using AWS CLI or SDKs, which adds complexity and effort. Adding these resources would ensure CloudFormation fully supports AWS Global Accelerator, making infrastructure management easier and more consistent.

### Other Details

https://docs.aws.amazon.com/global-accelerator/latest/api/API_Operations.html

Start with the AWS Global Accelerator API Operations page and the linked CreateCustomRoutingAccelerator and AllowCustomRoutingTraffic API references. Determine the coverage requirements for these missing Custom Routing resources; done means CloudFormation support is defined for the requested resources.

Written by the indexing model from the issue text.