Invalid E1019 error with nested Transform function

[szechyjs]

CloudFormation Lint Version

0.87.1

What operating system are you using?

Ubuntu

Describe the bug

Receive the following error E1019 Sub parameter should use a valid function for Resources/FooS3Bucket/Properties/BucketName/Fn::Sub however the following template is valid and builds just fine in CF.

Expected behavior

It should not be an error. I suspect Fn::Transform needs added to the list of allowable functions here: https://github.com/aws-cloudformation/cfn-lint/blob/main/src/cfnlint/rules/functions/Sub.py#L32

Reproduction template

BucketName: !Sub
  - "${EnvironmentLower}-foo-bar"
  - EnvironmentLower:
      Fn::Transform:
        Name: String
        Parameters:
          InputString: !Ref Environment
          Operation: Lower

[kddejong]

We may be able to create a workaround for this one but in general we are tracking transform issues here #476

[kddejong]

Fn Transform in a sub shouldn't toss an error anymore.