Add Rubocop rules for conventions

[joelhawksley]

Feature request

Add Rubocop rules for the conventions specified in the README.

Motivation

Having Rubocop rules for ViewComponent conventions will help users of the gem implement components using recommended best practices.

[lfalcao]

@joelhawksley as the project uses rubocop-github we only need to see .rubocop.yml to discover which files/cops are being used. Adding all rules into README, will only mess it and it's one more place for taking care.

Maybe related: #964

[joelhawksley]

I think we can close this 👍🏻

[andyw8]

This is an old discussion, but for the benefit of anyone who stumbles across it: https://github.com/andyw8/rubocop-view_component