TOML configuration file support

[TOML](https://toml.io/en/) is another configuration file format that is a little simpler to read and has a learning curve that's a bit less steep than YAML.

It would be great if we could use either format for the config files. There are existing libraries for reading a TOML file into a dictionary. So ideally the 2 formats could be interchangeable. Perhaps there could be an option to make the config files TOML-only, YAML-only, or either one depending on the file extension.

Is anybody else interested in this?