sphinx: Ensure cog_before_invoke has docstring to eliminate error.

inatcog/inatcog.py

@@ -128,6 +128,7 @@ def __init__(self, bot: commands.Bot):
         self._ready_event: asyncio.Event = asyncio.Event()
 
     async def cog_before_invoke(self, ctx: commands.Context):
+        """Initialization before cog is invoked."""
         await self._ready_event.wait()
 
     async def initialize(self) -> None: