[Best Practices] Add check for TimeSeries unit follows CMIXF-12 convention

[weiglszonja]

Motivation

WIP
Proposing a new check for TimeSeries that checks if unit formatting complies with the CMIXF-12 convention.
#208

How to test the behavior?

Show here how to reproduce the new behavior (can be a bug fix or a new feature)

Checklist

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[weiglszonja]

Double check what can and cannot be changed for units

[weiglszonja]

lexer.tokenize() a generator object, when a bad character is found it immediately raises an error. e.g.

tokens = lexer.tokenize("ta")
next(tokens) 

would return the recognized token value for unit t
Token(type='UNITC', value='t', lineno=1, index=0)

next(tokens)
would return:
{ValueError}Line 1: Bad character 'a'

[weiglszonja]

This is not TimeSeries but I thought could be good to include for example for representing degrees?

[CodyCBakerPhD]

CompassDirection is more typical for that as an example (be sure to include radians as well)

[codecov-commenter]

Codecov Report

Merging #281 (8964521) into dev (06622b7) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #281      +/-   ##
==========================================
+ Coverage   93.95%   94.02%   +0.06%     
==========================================
  Files          20       20              
  Lines        1026     1037      +11     
==========================================
+ Hits          964      975      +11     
  Misses         62       62              

Flag	Coverage Δ
unittests	94.02% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
nwbinspector/checks/time_series.py	97.77% <100.00%> (+0.71%)	⬆️

[bendichter]

can we hold off on this? I don't know if we want to use CMIXF