Extended MagicFilter with aiogram-specific operation (#759)

* Extend MagicFilter with aiogram-specific operation

* Added tests

* Added changes annotation and update docs

tests/test_utils/test_magic_filter.py

@@ -0,0 +1,21 @@
+from dataclasses import dataclass
+from re import Match
+
+from aiogram import F
+from aiogram.utils.magic_filter import MagicFilter
+
+
+@dataclass
+class MyObject:
+    text: str
+
+
+class TestMagicFilter:
+    def test_operation_as(self):
+        magic: MagicFilter = F.text.regexp(r"^(\d+)$").as_("match")
+
+        assert not magic.resolve(MyObject(text="test"))
+
+        result = magic.resolve(MyObject(text="123"))
+        assert isinstance(result, dict)
+        assert isinstance(result["match"], Match)