Where do I place additional files?

Where do I place additional static data files so that they will be part of the module such as .json, .xml, .png etc.?

I.e. files that I would normally specify in the .psd1 file of the module.

~~~
# List of all files packaged with this module
# FileList = @()
~~~

I tried adding a file by hand in the output folder, hoping that `.\build.ps1 pack` would include it and then including it in the manifest file, but that failed as pack cleans the output folder first.

~~~
# List of all files packaged with this module
FileList = @('files\data.json')
~~~

> ERROR: Module manifest file validation failed with error: The specified FileList entry 'files\data.json' in the module manifest '...\CompleteSample\output\module\CompleteSample\0.0.1\CompleteSample.psd1' is invalid. Try again after updating this entry with valid values..

The `Test-ModuleManifest .\CompleteSample.psd1` tests successfully if run before pack removes my added file from the output folder.