Refactor near-infrared reflectance calculator

[pnuu]

This PR does some refactoring to pyspectral.near_infrared_reflectance module.

• Closes #xxxx
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

❌ Patch coverage is 83.90805% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.34%. Comparing base (d4ea15a) to head (06eefad).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
pyspectral/near_infrared_reflectance.py	83.90%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #264      +/-   ##
==========================================
+ Coverage   90.28%   90.34%   +0.05%     
==========================================
  Files          22       22              
  Lines        2523     2538      +15     
==========================================
+ Hits         2278     2293      +15     
  Misses        245      245              

Flag	Coverage Δ
unittests	90.34% <83.90%> (+0.05%)	⬆️

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[adybbroe]

Thanks @pnuu nice work. Haven't carefully checked everything yet, it is some re-arrangements, so just wonder if you are confident with the test coverage of all this?

Also, perhaps you saw there was some discussion recently about the "nir" and "near infrared" here, as it is a bit mis-leading and strictly not true, as we are operating with what is normally termed the mid-wave IR range. SO, should this be part of this re-factoring, or rather another one?

I guess that changing the name of functions will break compatibility in Satpy for instance, so should probably go in another PR...

[pnuu]

The coverage report says 14 lines miss coverage. Haven't looked too closely, but likely something I don't have much experience with.

The naming change with associated aliases and deprecation warnings is certainly a separate PR.