Add excalidraw API and data representation diagrams

[dougbrn]

Change Description

Closes #255
Closes #412

Solution Description

Adds drawings from excalidraw, as well as the original files for reproducibility/modification

Code Quality

• I have read the Contribution Guide and agree to the Code of Conduct
• My code follows the code style of this project
• My code builds (or compiles) cleanly without any errors or warnings
• My code contains relevant comments and necessary documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.30%. Comparing base (39a4681) to head (143413d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #456   +/-   ##
=======================================
  Coverage   97.30%   97.30%           
=======================================
  Files          19       19           
  Lines        2156     2156           
=======================================
  Hits         2098     2098           
  Misses         58       58           

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[github-actions]

Before [39a4681]	After [e55bf06]	Ratio	Benchmark (Parameter)
592±100ms	645±90ms	1.09	benchmarks.ReadFewColumnsHTTPS.time_run
1.18G	1.23G	1.04	benchmarks.ReadFewColumnsS3.peakmem_run
30.0±1ms	30.8±1ms	1.03	benchmarks.AssignSingleDfToNestedSeries.time_run
257M	258M	1.01	benchmarks.AssignSingleDfToNestedSeries.peakmem_run
66.9±0.9ms	67.7±3ms	1.01	benchmarks.CountNestedBy.time_run
10.6±0.09ms	10.7±0.1ms	1.01	benchmarks.NestedFrameAddNested.time_run
179M	180M	1.01	benchmarks.ReadFewColumnsHTTPS.peakmem_run
49.4±0.1ms	50.1±0.3ms	1.01	benchmarks.ReassignHalfOfNestedSeries.time_run
105M	105M	1	benchmarks.NestedFrameAddNested.peakmem_run
110M	110M	1	benchmarks.NestedFrameQuery.peakmem_run

Click here to view all benchmarks.