Add documentation for how to use with Numpy and Pandas

[matt035343]

Closes #90 and #352

I apologize for the commit message. I forgot to change it before comitting.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
dataclasses_json
cfg.py	51	4	92%	80, 84–86
core.py	235	10	96%	38–41, 51, 64, 66, 81, 83, 169, 197
mm.py	202	30	85%	33–36, 42–45, 53–56, 62–65, 88, 161–162, 167, 171, 175, 180, 184, 188, 196, 202, 207, 216, 221, 226, 235, 244–251
stringcase.py	25	3	88%	59, 76, 97
undefined.py	143	2	99%	24, 38
utils.py	128	36	72%	11–24, 44–49, 60–64, 74, 99–100, 108–109, 124–132, 158, 177, 202
tests
entities.py	226	2	99%	229, 235
test_annotations.py	81	42	48%	50–67, 78–102, 106–122
test_api.py	142	4	97%	88, 99, 139–140
test_str_subclass.py	22	1	95%	9
test_union.py	98	10	90%	87–94, 108–115
TOTAL	2486	144	94%

Tests	Skipped	Failures	Errors	Time
292	3 💤	0 ❌	0 🔥	5.443s ⏱️

[matt035343]

@george-zubrienko Please approve again, reviews are reset upon commit apparently