Nudge about standard extensions

[tejasbubane]

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

Although it has been long time since we extracted rubocop-rails from core some users never discover our extensions. I have seen quite a few modern Rails projects using only rubocop.

Describe the solution you'd like

I would like when rubocop is run, it recognizes and prints a log message suggesting standard plugins like rubocop-rails, rspec, minitest, rake, sequel - whichever applicable to the project.

An option to disable this message.

Describe alternatives you've considered

A generic log message suggesting to have a look at our extensions.

[bbatsov]

Good idea. Shouldn't be hard to implement it.

[dvandersluis]

I'm taking a stab at this.