IPywidgets do not work with fastapi server

[singharpit94]

Hi,

Thanks for adding support for panel with fastapi, I have an application which also renders IPywidgets and I see that they do not work with fast api server while the same work with panel serve. Is this expected?

Reproducer code

import panel as pn

from fastapi import FastAPI
import ipywidgets as widgets
from panel.io.fastapi import add_application

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

@add_application('/panel', app=app, title='My Panel App')
def create_panel_app():
    slider = widgets.IntSlider(
        value=3,
        min=0,
        max=10,
        step=1,
        description='Slider:',
        disabled=False,
        continuous_update=False,
        orientation='horizontal',
        readout=True,
        readout_format='d'
    )

    return slider

Can we add support for IPywidgets?