docs: Update changelog

CHANGELOG.md

@@ -9,8 +9,22 @@ Check our main [developer changelog](https://developer.paddle.com/?utm_source=dx
 ## [Unreleased]
 
 ### Added
+- Added simulation API support [related changelog](https://developer.paddle.com/changelog/2024/webhook-simulator?utm_source=dx&utm_medium=paddle-python-sdk)
+  - `Client.simulations.create`
+  - `Client.simulations.update`
+  - `Client.simulations.get`
+  - `Client.simulations.list`
+  - `Client.simulation_runs.create`
+  - `Client.simulation_runs.get`
+  - `Client.simulation_runs.list`
+  - `Client.simulation_run_events.replay`
+  - `Client.simulation_run_events.get`
+  - `Client.simulation_run_events.list`
 - Added `traffic_source` property to `paddle_billing.Entities.NotificationSetting` entity
 
+### Fixed
+- `paddle_billing.Notifications.Entities.Subscription` and `paddle_billing.Notifications.Entities.SubscriptionCreated` `current_billing_period` would return `None` if `billing_details` was `None`. `current_billing_period` will now return `TimePeriod` when set.
+
 ## 1.1.1 - 2024-11-14
 
 ### Fixed