Update CHANGELOG

CHANGELOG.md

@@ -10,7 +10,11 @@
   - the `HR` country (Croatia) is now mapped to `EUR` (Euro)
 - `PDOProviderConfiguration` now has a proper constructor, and its properties are no longer public
 - `PDOProviderConfiguration` now throws exceptions in the constructor when configuration is invalid
-- All documented union types are now strongly typed; you may only be affected if you have a custom `ExchangeRateProvider` implementation
+- All documented union types are now strongly typed<sup>*</sup>
+
+<sup>* You may be affected if you have a custom `ExchangeRateProvider` implementation (in which case you will need to update your method signature),
+or if you were passing `Stringable` objects to `of()` or any of the methods  internally calling `of()`, with `strict_types` enabled.
+You can fix this by casting `Stringable` objects to `string` first.</sup>
 
 ## [0.7.1](https://github.com/brick/money/releases/tag/0.7.1) - 2023-01-16