Feature Request: ability to load CreatorConfigs from external file

[melithine]

I have a few different versions of my config.json, and I keep a separate JSON files containing my custom filename formats for different creators, using text names for the creators instead of the {username} macro so that the created files can be directly used in my Plex library. Right now, I have a script that combines my desired config-someprofile.json source with the custom filename json file into the actual config.json, before it then launches the Docker container. This step takes a bit to merge the JSON files, so it would be nice if ofdl supported loading that directly.