add user_hello dialog

app/dialogs/user_dialog.py

@@ -0,0 +1,22 @@
+from aiogram import Router
+from aiogram.fsm.state import State, StatesGroup
+from aiogram_dialog import Dialog, DialogManager, StartMode, Window
+from aiogram_dialog.widgets.text import Format
+
+from app.utils.getters import username_getter
+
+
+class StartSG(StatesGroup):
+    start = State()
+
+
+start_dialog = Dialog(
+    Window(
+        Format("Hello, {username}"),
+        getter=username_getter,
+        state=StartSG.start
+    )
+)
+
+router = Router(name="user_dialogs")
+router.include_router(start_dialog)