Support overriding dependabot updates

[nikeokoronkwo]

I was trying to override the dependabot updates to run "monthly" rather than "weekly",

github:
  dependabot:
    updates:
      - package-ecosystem: "pub"
        directory: common
        schedule:
          interval: "monthly"

I noticed that the resulting dependabot.yml file contained both weekly and monthly updates (for the same package) rather than the user-defined option overriding the default option (i.e having only monthly updates)?

Is it possible to override the dependabot config for specific packages, and if not, is it possible to provide such options?