Did some refactor, add YouTube as search variant

bot/handlers/inline_song/__init__.py

@@ -0,0 +1,10 @@
+from aiogram import Router
+
+from . import on_inline_spotify, on_inline_deezer, on_inline_youtube
+
+router = Router()
+router.include_routers(
+    on_inline_spotify.router,
+    on_inline_deezer.router,
+    on_inline_youtube.router,
+)