Describe the solution you'd like
When invoking Boilerplate it should optionally provide an output (list) of all the files it created.

For instance, a cli flag could be added: --file-manifest

Additional context
This would be a feature to help address this terragrunt issue. Currently Terragrunt runs an hclfmt on the entire output/working directory to ensure all generated files are properly formatted. This is problematic due to reasons described in that ticket. In order to address the issue Terragrunt needs to know which files were generated. Terragrunt itself however has no direct way of figuring out which files were created by Boilerplate. The most logical way to proceed is to add the above functionality, so that terragrunt can consume the Boilerplate output and then format the files listed.