Call `new DataTable` on tables only

[mwouts]

Closes #317

[github-actions[bot]]

Thank you for making this pull request.

Did you know? You can try it on Binder: .

Also, the version of ITables developed in this PR can be installed with pip:

pip install git+https://github.com/mwouts/itables.git@select_tables_only

(this requires nodejs, see more at Developing ITables)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.94%. Comparing base (25b58de) to head (b1554f1). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #318 +/- ## ========================================== - Coverage 93.95% 93.94% -0.01% ========================================== Files 28 28 Lines 1339 1338 -1 ========================================== - Hits 1258 1257 -1 Misses 81 81 ``` | [Flag](https://app.codecov.io/gh/mwouts/itables/pull/318/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Marc+Wouts) | Coverage Δ | | |---|---|---| | [](https://app.codecov.io/gh/mwouts/itables/pull/318/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Marc+Wouts) | `93.94% <100.00%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Marc+Wouts#carryforward-flags-in-the-pull-request-comment) to find out more.

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