init upgrading guide to v3

Author: vdusek

docs/04_upgrading/upgrading_to_v2.md

@@ -3,7 +3,7 @@ id: upgrading-to-v2
 title: Upgrading to v2
 ---
 
-This page summarizes most of the breaking changes between Apify Python SDK v1.x and v2.0.
+This page summarizes the breaking changes between Apify Python SDK v1.x and v2.0.
 
 ## Python version support
 
@@ -12,7 +12,7 @@ Support for Python 3.8 has been dropped. The Apify Python SDK v2.x now requires
 ## Storages
 
 - The SDK now uses [crawlee](https://github.com/apify/crawlee-python) for local storage emulation. This change should not affect intended usage (working with `Dataset`, `KeyValueStore` and `RequestQueue` classes from the `apify.storages` module or using the shortcuts exposed by the `Actor` class) in any way.
-- There is a difference in the `RequestQueue.add_request` method: it accepts an `apify.Request` object instead of a free-form dictionary. 
+- There is a difference in the `RequestQueue.add_request` method: it accepts an `apify.Request` object instead of a free-form dictionary.
     - A quick way to migrate from dict-based arguments is to wrap it with a `Request.model_validate()` call.
     - The preferred way is using the `Request.from_url` helper which prefills the `unique_key` and `id` attributes, or instantiating it directly, e.g., `Request(url='https://example.tld', ...)`.
     - For simple use cases, `add_request` also accepts plain strings that contain an URL, e.g. `queue.add_request('https://example.tld')`.

docs/04_upgrading/upgrading_to_v3.md

@@ -0,0 +1,18 @@
+---
+id: upgrading-to-v2
+title: Upgrading to v2
+---
+
+This page summarizes the breaking changes between Apify Python SDK v2.x and v3.0.
+
+## Python version support
+
+Support for Python 3.9 has been dropped. The Apify Python SDK v3.x now requires Python 3.10 or later. Make sure your environment is running a compatible version before upgrading.
+
+## Storages
+
+<!-- TODO -->
+
+## Storage clients
+
+<!-- TODO -->