Add capability to update default dests with the config

[Borito185]

Currently, the prebuilt_commands.json is only applied once when the mod is first loaded. This means that any additions or changes are only applied to first-time users of the mod.

I want to keep the ability for users to modify the list and use their own version, but we should be able to make changes to this list, preferably automatically. It would be nice if we could somehow only load the differences.