Auto-format the auto-generated manifest YML

[dblock]

Is your feature request related to a problem? Please describe

When a new manifest is generated by the manifests workflow it's strangely formatted. When we try to make changes to it by hand we end up auto-formatting it very differently, e.g. #1449

Describe the solution you'd like

Write new manifests that are formatted as if they were authored by the default auto-formatter in VSCode (or other editor).

Describe alternatives you've considered

No response

Additional context

No response

[peternied]

An alternative approach, we could apply a check / auto-formatter on all manifest.yml files.