Docs say ChatKitServer.action() is "async def", but it's actually just normal "def"

[paul-felt]

The official docs give guidance to handle actions by overriding ChatKitServer.action with an async def:

chatkit-python/docs/actions.md

Line 55 in a6c216b

async def action(

But in the actual code it's just a normal def:

chatkit-python/chatkit/server.py

Line 299 in a6c216b

def action(

This causes errors if you try to follow the docs. Should either update the docs or else change the action to an async def