docs(format): update example code with new report structure

[byCedric]

Description

The new formatters feature introduced the new report-structure. This structure is created within the CLI and passed to the formatter to produce a nice string.

Motivation and Context

I'd recon if people want to create their own formatter, they probably checkout the default @commitlint/format.

Usage examples

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.