`ROT13`: optimized initialization and removed magic numbers (#1702)
`ROT13`: optimized initialization and removed magic numbers (#1702)

### Changes:

- Using `Dictionary.init(minimumCapacity:)` to allocate the necessary size initially instead of growing when adding data to it
- Defined `uppercase` in terms of `lowercase`
- Removed magic `13` and `26` numbers
RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios,RevenueCat/purchases-ios