[Request] Generate policy file when using scaffolding

Hi,

It would be great if running

rails g scaffold Model
rails g controller Model

would actually generate an empty policy file that inherits from ApplicationPolicy.

As a bonus, for resources scaffolding, maybe we could implements all CRUD actions and defaults to false.

Linking this in case it helps the implementation https://gist.github.com/annikoff/331f785aa7a207a7945b1eca6eff526b

[Burgestrand]

FYI this came up again with #785, so I suggested moving that into here.

[hoverjet]

Hi, I've added #794