correct datum project import examples

[jihyeonyi]

Summary

1. Correct documents to use correctly use 'datum project import' command.
2. Add filtering example to filter out items containing annotations only. (Filter out items without annotations #1208)

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (231f6d9) 80.07% compared to head (1b54b1d) 80.08%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1210   +/-   ##
========================================
  Coverage    80.07%   80.08%           
========================================
  Files          268      268           
  Lines        29865    29865           
  Branches      5846     5846           
========================================
+ Hits         23915    23916    +1     
  Misses        4617     4617           
+ Partials      1333     1332    -1     

Flag	Coverage Δ
macos-11_Python-3.8	79.19% <ø> (ø)
ubuntu-20.04_Python-3.8	80.07% <ø> (+<0.01%)	⬆️
windows-2022_Python-3.8	80.04% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[vinnamkim]

LGTM.