Notarization option --api-key-file is not configurable via configuration file

[basilevs]

I can't find a way to move static options (those that never change) of rcodesign from command line to configuration file or environment.

At the moment, I'm interested in --api-key-file for notarization and --for-notarization for sign.

[indygreg]

We don't yet have config file support for notarization.

The config file schema is designed for extensions like this. We could just add a notarize table or similar for providing settings like --api-key-file.

I would accept a PR to add the missing functionality if someone wants to contribute it.