Generated yaml should be indented according to best practice

[AndreasPelzer]

This is just a suggestion for small improvement!

Current output (missing indentation):

---
groups:
- name: sonarqube critical alerts
    interval: 30m

Expected output (with indentation):

---
groups:
  - name: sonarqube critical alerts
    interval: 30m

Advantage:

• readability
• linter will not complain