Typed data (#1647)

* Add TypedDict support for middleware context data

Introduced `MiddlewareData` and associated TypedDicts to type-hint middleware context data. Updated documentation to include usage examples and guidelines for extending the default middleware data. Also adjusted coverage configuration to exclude the new data module.

* Added more docstrings

* Typo fixes

docs/dispatcher/dependency_injection.rst

@@ -70,3 +70,61 @@ The last way is to return a dictionary from the filter:
 .. literalinclude:: ../../examples/context_addition_from_filter.py
 
 ...or using :ref:`MagicFilter <magic-filters>` with :code:`.as_(...)` method.
+
+
+Using type hints
+================
+
+.. note::
+
+    Type-hinting middleware data is optional and is not required for the correct operation of the dispatcher.
+    However, it is recommended to use it to improve the readability of the code.
+
+You can use type hints to specify the type of the context data in the middlewares, filters and handlers.
+
+The default middleware data typed dict can be found in :class:`aiogram.dispatcher.middlewares.data.MiddlewareData`.
+
+In case when you have extended the context data, you can use the :class:`aiogram.dispatcher.middlewares.data.MiddlewareData` as a base class and specify the type hints for the new fields.
+
+.. warning::
+
+    If you using type checking tools like mypy, you can experience warnings about that this type hint against Liskov substitution principle in due stricter type is not a subclass of :code:`dict[str, Any]`.
+    This is a known issue and it is not a bug. You can ignore this warning or use :code:`# type: ignore` comment.
+
+Example of using type hints:
+
+.. code-block:: python
+
+    from aiogram.dispatcher.middlewares.data import MiddlewareData
+
+
+    class MyMiddlewareData(MiddlewareData, total=False):
+        my_custom_value: int
+
+
+    class MyMessageMiddleware(BaseMiddleware):
+        async def __call__(
+            self,
+            handler: Callable[[Message, MyMiddlewareData], Awaitable[Any]],
+            event: Message,
+            data: MyMiddlewareData,
+        ) -> Any:
+            bot = data["bot"]  # <-- IDE will show you that data has `bot` key and its type is `Bot`
+
+            data["my_custom_value"] = bot.id * 42  # <-- IDE will show you that you can set `my_custom_value` key with int value and warn you if you try to set it with other type
+            return await handler(event, data)
+
+
+Available context data type helpers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: aiogram.dispatcher.middlewares.data.MiddlewareData
+    :members:
+    :undoc-members:
+    :member-order: bysource
+
+
+.. autoclass:: aiogram.dispatcher.middlewares.data.I18nData
+    :members:
+    :undoc-members:
+    :member-order: bysource