Added add_periodic_callback coroutine typing

The `add_periodic_callback` method only had the `Callable` type hint while it also supports asyncio functions. This adds that type hint so `pyright` won't complain anymore :)

panel/io/state.py

@@ -19,7 +19,7 @@
 from functools import partial
 from typing import (
     TYPE_CHECKING, Any, Callable, ClassVar, Dict, Iterator as TIterator, List,
-    Optional, Tuple, Union,
+    Optional, Tuple, Union, Coroutine,
 )
 from urllib.parse import urljoin
 from weakref import WeakKeyDictionary
@@ -379,8 +379,9 @@ def as_cached(self, key: str, fn: Callable[[], None], ttl: int = None, **kwargs)
         return ret
 
     def add_periodic_callback(
-        self, callback: Callable[[], None], period: int=500,
-        count: Optional[int] = None, timeout: int = None, start: bool=True
+        self, callback: Callable[[], None] | Coroutine[Any, Any, None],
+        period: int=500, count: Optional[int] = None, timeout: int = None,
+        start: bool=True
     ) -> PeriodicCallback:
         """
         Schedules a periodic callback to be run at an interval set by