💡 update docstring

nonebot/permission.py

@@ -20,6 +20,20 @@ if TYPE_CHECKING:
 
 
 class Permission:
+    """
+    :说明:
+
+      ``Matcher`` 规则类，当事件传递时，在 ``Matcher`` 运行前进行检查。
+
+    :示例:
+
+    .. code-block:: python
+
+        Permission(async_function) | sync_function
+        # 等价于
+        from nonebot.utils import run_sync
+        Permission(async_function, run_sync(sync_function))
+    """
     __slots__ = ("checkers",)
 
     def __init__(