yarn start does not run under "pre-built-app" example widget

[mycollablab]

Describe the bug
error when running 'yarn start'

To Reproduce
Steps to reproduce the behavior:

1. copy repo
2. go to pre-built-app example folder
3. run yarn
4. run yarn start

Expected behavior
node server starts

Screenshots

prebuild-app-widget % yarn start
yarn run v1.22.19
error Command "start" not found.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Fix:
Add "start": "webpack-dev-server --mode development" under "
scripts" in package.json