Laravel Cashier upgrade rules

[GeniJaho]

Can we include rules to upgrade Cashier to later versions like 13 and 14 in this repository? At least to handle the boring method renames and whatever work that can be automated.

Since it's a first-party Laravel package it would make sense to include it in this repo, but while adding new classes that are Cashier-specific, the Rector rules become bloated and hard to navigate.

A solution could be to prepend the rules with the Cashier prefix, for example, CashierStripeOptionsToStripeRector.

Or would a new repository be a better idea?

[driftingly]

I think prefixing is fine, groups related classes and allows for easy scanning.

[driftingly]

Closed by #103