Update upgrading guide

Author: janbuchar

docs/04-upgrading/upgrading_to_v20.md

@@ -19,7 +19,9 @@ Attributes suffixed with `_millis` were renamed to remove said suffix and have t
 
 ## Actor
 
-The `Actor.main` method has been removed as it brings no benefits compared to using `async with Actor`.
+- The `Actor.main` method has been removed as it brings no benefits compared to using `async with Actor`.
+- The `Actor.add_webhook`, `Actor.start`, `Actor.call` and `Actor.start_task` methods now accept instances of the `apify.Webhook` model instead of an untyped `dict`.
+- `Actor.start`, `Actor.call`, `Actor.start_task`, `Actor.set_status_message` and `Actor.abort` return instances of the `ActorRun` model instead of an untyped `dict`.
 
 ## Scrapy integration