Adjust opt-in to be copy & pasteable into config file

[colszowka]

Is your feature request related to a problem? Please describe.

The recently adjusted opt-in behaviour to new cops comes with a warning printed on rubocop runs that lists all not-yet configured cops, like this:

The following cops were added to RuboCop, but are not configured. Please set Enabled to either `true` or `false` in your `.rubocop.yml` file:
 - Lint/DuplicateElsifCondition (0.88)
 - Lint/MixedRegexpCaptureTypes (0.85)
 - Style/AccessorGrouping (0.87)

Describe the solution you'd like

As I usually find myself wanting to opt-in to all new cops I would appreciate if the output would be formatted in a way that is directly copy&pasteable. I tried this out locally by adjusting the corresponding code in config loader to print like this instead:

The following cops were added to RuboCop, but are not configured. Please set Enabled to either `true` or `false` in your `.rubocop.yml` file:
Lint/DuplicateElsifCondition: # (new in 0.88)
  Enabled: true
Lint/MixedRegexpCaptureTypes: # (new in 0.85)
  Enabled: true
Style/AccessorGrouping: # (new in 0.87)
  Enabled: true

I would be willing to send a PR with the corresponding changes, but wanted to check in whether this is a change that would be accepted.

Thanks for the extremely useful tool!

[marcandre]

I would be willing to send a PR

Yes please! 👍 😄

[colszowka]

@marcandre Here we go: #8414