dov/dev/notes: Add note about live reloads in restricted discovery mode.

This describes a couple of options for extending the config reloading logic to support watching for changes in the restricted_disovery.key_dirs directories.

Note: the options we have here are, in a sense, two extremes

• one is about refactoring some of the existing code into a reusable component, and leaving most of the configuration logic unchanged
• the other involves rethinking the entire config watching/reloading mechanism to support watching for changes in arbitrary directories

I am leaning towards the simpler option, because I'm not sure the other one is worth the added complexity (we currently only have a single use case for it).