Dependabot-2.0 schema forbids groups with exclude-patterns only

[eisclimber]

Area with issue?

JSON Schema

✔️ Expected Behavior

Groups containing only an "exclude-patterns"-property are recognized as valid, as they are accepted by Dependabot.
An example project for this behavior can be found here.

❌ Actual Behavior

The schema does not recognize the group as correct and displays the error: Missing property "dependency-type".yaml-schema: Package Ecosystem.

YAML or JSON file that does not work.

This dependabot file is considered invalid by the schema, but is accepted by GitHub.

version: 2
updates:
- package-ecosystem: "github-actions"
  directory: "/"
  schedule:
    interval: "monthly"
  groups:
    exclude-group:
      exclude-patterns:
        - .github/workflows/exclude-*.yml

IDE or code editor.

None

Are you making a PR for this?

Yes, I will create a PR.