Add blog post about core config move (#2433)

* Add blog post about core config move

* Update blog/2024-10-31-core-config-moved.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update blog/2024-10-31-core-config-moved.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Martin Hjelmare <[email protected]>

* Update 2024-10-31-core-config-moved.md

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Martin Hjelmare <[email protected]>

blog/2024-10-31-core-config-moved.md

@@ -0,0 +1,32 @@
+---
+author: Erik Montnemery
+authorURL: https://github.com/emontnemery
+title: "The core config class has been moved"
+---
+
+### Summary of changes
+
+The definition of the core config class, an instance of which is available as [`hass.config`](https://developers.home-assistant.io/docs/dev_101_hass/#the-hass-object) has been moved from `homeassistant/core.py` to `homeassistant/core_config.py`. The move was done to make it easier to read and understand the core code. Custom integrations which currently import `Config` from `homeassistant.core` need to be updated to instead import from `homeassistant.core_config`.
+
+:::info
+Normally, integrations won't need to use the core `Config` class. But there's been custom integrations that have incorrect type annotations where the `config` object passed to the integration's `async_setup` is specified as a `Config` instance:
+```py
+from homeassistant.core import Config
+
+async def async_setup(hass: HomeAssistant, config: Config) -> bool:
+    """Set up the integration."""
+```
+
+A correct type annotation would be like this:
+```py
+from homeassistant.helpers.typing import ConfigType
+
+async def async_setup(hass: HomeAssistant, config: ConfigType) -> bool:
+    """Set up the integration."""
+```
+:::
+
+
+### Backwards compatibility
+
+Until Home Assistant Core 2025.11, it's possible to import from `homeassistant.core`, and doing so will log a warning asking users to open an issue on the custom integration's bug tracker.