feat: Add event data to MIGRATING event

Author: fnesveda

Diff for: sources/platform/actors/development/programming_interface/system_events.md

@@ -32,7 +32,7 @@ The following table outlines the system events available:
 | Event name     | Payload | Description |
 | -------------- | ------- | ----------- |
 | `cpuInfo`      | `{ isCpuOverloaded: Boolean }` | Emitted approximately every second, indicating whether the Actor is using maximum available CPU resources. |
-| `migrating`    | N/A | Signals that the Actor will soon migrate to another worker server on the Apify platform. |
+| `migrating`    | `{ timeRemainingSecs: Float }` | Signals that the Actor will soon migrate to another worker server on the Apify platform. |
 | `aborting`     | N/A | Triggered when a user initiates a graceful abort of an Actor run, allowing time for cleanup. |
 | `persistState` | `{ isMigrating: Boolean }` | Emitted at regular intervals  (default: _60 seconds_) to notify Apify SDK components to persist their state. |