id:sue445さんの記事を参考にDependabotの設定ファイルを置いてみた。
こんな内容にした:

# c.f. https://dependabot.com/docs/config-file/
version: 1

update_configs:
  - package_manager: "ruby:bundler"
    directory: "/"
    update_schedule: "daily"
    allowed_updates:
      - match:
          update_type: "all"
    automerged_updates:
      - match:
          dependency_type: "development"
          update_type: "all"
      - match:
          dependency_type: "production"
          update_type: "semver:patch"
    version_requirement_updates: "off"
  - package_manager: "javascript"
    directory: "/"
    update_schedule: "daily"
    allowed_updates:
      - match:
          update_type: "all"
    automerged_updates:
      - match:
          dependency_type: "development"
          update_type: "all"
      - match:
          dependency_type: "production"
          update_type: "semver:patch"
    version_requirement_updates: "off"