Add CI for jupyter notebook example `workflow_by_code.ipynb`

Feature Description

CI that it can't detect the errors in the report. So I think it would be better to add such a check in our CI. (It may be some command like jupyter nbconvert workflow_by_code.ipynb)

Please refer to this comment. https://github.com/microsoft/qlib/pull/1267#issuecomment-1230072848

Motivation

1. Application scenario
2. Related works (Papers, Github repos etc.):
3. Any other relevant and important information:

Alternatives

Additional Notes