Add an option to enforce subscription variable names using finnish rule

First point is that I noticed that the project I’m currently working on has two standards for “Subscription” declarations: one that uses finnish notation and others that don’t, so I’d like to propose the addition of this option in finnish rule.

A trivial case that I’m seeing much is the use with @ngrx / component-store, which generally looks like this:

class MyStore extends ComponentStore<State> {
  // `myEffect` is typed as `Subscription`.
  readonly myEffect = this.effect(trigger$ => trigger$.pipe())
}

In this case, I’d like to enforce myEffect to be myEffect$. Maybe it could be useful to implements it also in no-finnish so other teams can avoid this notation even for Subscription.

The second point is another thing that I also noticed that sometimes the finnish notation is misused, for example in places that do not use Observables or something like that, but I don’t know if it’s in the scope of this rule.

[timdeschryver]

I don’t think this makes sense. A component store effect is just a method that returns a void or a Subscription, the return type of the attached snipped would be const myEffect: () => void.

[cartant]

In 3.1.0, the finnish rule now has a strict option that will effect failures for non-Observable identifiers that have a $ suffix.