Feature Request: accept async functions in on_kernel_start

[iisakkirotko]

Feature Request

• The requested feature would break current behaviour
• I would be interested in opening a PR for this feature

What problem would this feature solve? Please describe.

For certain functionality that you might want to execute on kernel start, you need to call asynchronous functions. It would be useful to accept these for solara.lab.on_kernel_start

Describe the solution you'd like

The cleanest would be simply allowing

@solara.lab.on_kernel_start
async def init():
    await database.connect()

    async def cleanup():
        await database.disconnect()
    return cleanup