Documentation notebook for groupby

[Graciaaa3]

Adding a documentation notebook for groupby usage within nested-pandas. The notebook contains:

• working and failing cases of basic aggregations on NestedFrame after groupby.
• a section discussing the type preservation with groupby object and indexing.
• some potential use of apply after groupby.

closes #333

Change Description

• My PR includes a link to the issue that I am addressing

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.27%. Comparing base (d82a63d) to head (1ebedec).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #396   +/-   ##
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  Coverage   97.27%   97.27%           
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  Files          19       19           
  Lines        2089     2089           
=======================================
  Hits         2032     2032           
  Misses         57       57           

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[github-actions]

Before [ebe6315] <v0.6.2>	After [6067b10]	Ratio	Benchmark (Parameter)
258M	262M	1.02	benchmarks.ReassignHalfOfNestedSeries.peakmem_run
59.8±0.1ms	60.2±0.8ms	1.01	benchmarks.CountNestedBy.time_run
11.1±0.1ms	11.2±0.2ms	1.01	benchmarks.NestedFrameAddNested.time_run
10.7±0.1ms	10.8±0.1ms	1.01	benchmarks.NestedFrameQuery.time_run
1.19±0.01ms	1.21±0.01ms	1.01	benchmarks.NestedFrameReduce.time_run
179M	181M	1.01	benchmarks.ReadFewColumnsHTTPS.peakmem_run
1.98±0.02s	1.99±0.05s	1.01	benchmarks.ReadFewColumnsS3.time_run
135M	135M	1	benchmarks.CountNestedBy.peakmem_run
257M	254M	0.99	benchmarks.AssignSingleDfToNestedSeries.peakmem_run
33.4±0.8ms	33.0±1ms	0.99	benchmarks.AssignSingleDfToNestedSeries.time_run

Click here to view all benchmarks.

[dougbrn]

I added some review comments above, but overall I think the structure of this looks really good @Graciaaa3! As you probably see, the docs builds aren't passing and I suspect that's due to the min/max/mean case in your notebook which is supposed to fail. I added a comment with some potential solutions to that.

[dougbrn]

Also, make sure to add an entry for this notebook into the tutorials.rst file so that this is navigable on the readthedocs site

[dougbrn]

Looks great, thank you!

[gitosaurus]

Looks good!