Adding additional configuration folder

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Hi,
I want to include an additional folder for my config files.
I used this option
additionalAppResources = "src/main/external-config"
all the config files get copied to the 'app' folder.

Now I only need to add them to the classPath, so my configuration builder can find them.
How can I add additional folder/files to the app.classpath in the app.cfg?