`read_commandline` supports polars engine

[samukweku]

PR Description

Please describe the changes proposed in the pull request:

• read_commandline now supports polars

**This PR relates to #1352 **

import janitor as jn
jn.read_commandline('unzip -p ../Downloads/iris.zip', engine='polars')
Out[12]: 
shape: (150, 5)
┌──────────────┬─────────────┬──────────────┬─────────────┬───────────┐
│ sepal_length ┆ sepal_width ┆ petal_length ┆ petal_width ┆ species   │
│ ---          ┆ ---         ┆ ---          ┆ ---         ┆ ---       │
│ f64          ┆ f64         ┆ f64          ┆ f64         ┆ str       │
╞══════════════╪═════════════╪══════════════╪═════════════╪═══════════╡
│ 5.1          ┆ 3.5         ┆ 1.4          ┆ 0.2         ┆ setosa    │
│ 4.9          ┆ 3.0         ┆ 1.4          ┆ 0.2         ┆ setosa    │
│ 4.7          ┆ 3.2         ┆ 1.3          ┆ 0.2         ┆ setosa    │
│ 4.6          ┆ 3.1         ┆ 1.5          ┆ 0.2         ┆ setosa    │
│ 5.0          ┆ 3.6         ┆ 1.4          ┆ 0.2         ┆ setosa    │
│ …            ┆ …           ┆ …            ┆ …           ┆ …         │
│ 6.7          ┆ 3.0         ┆ 5.2          ┆ 2.3         ┆ virginica │
│ 6.3          ┆ 2.5         ┆ 5.0          ┆ 1.9         ┆ virginica │
│ 6.5          ┆ 3.0         ┆ 5.2          ┆ 2.0         ┆ virginica │
│ 6.2          ┆ 3.4         ┆ 5.4          ┆ 2.3         ┆ virginica │
│ 5.9          ┆ 3.0         ┆ 5.1          ┆ 1.8         ┆ virginica │
└──────────────┴─────────────┴──────────────┴─────────────┴───────────┘

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Relevant Reviewers

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• @ericmjl

[ericmjl]

🚀 Deployed on https://deploy-preview-1356--pyjanitor.netlify.app

[ericmjl]

@samukweku we're close with this one -- I think the line that is failing in test_readcommandline() is this one under the polars engine:

assert df.equals(dataframe)

Would you be kind enough to take a look at this particular error? I am quite sure it's got to do with the polars internal API, but that's one I'm not familiar enough with to know.

[ericmjl]

Also LGTM, thanks @samukweku!