Add user docs

[mdoucet]

Add user documentation that describes how to use the module.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.80203% with 26 lines in your changes missing coverage. Please review.

Project coverage is 85.77%. Comparing base (81e811a) to head (122769d).
Report is 33 commits behind head on next.

Files with missing lines	Patch %	Lines
reduction/lr_reduction/template.py	71.21%	19 Missing ⚠️
...eduction/lr_reduction/reduction_template_reader.py	90.69%	4 Missing ⚠️
reduction/lr_reduction/time_resolved.py	93.61%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next      #58      +/-   ##
==========================================
- Coverage   85.87%   85.77%   -0.10%     
==========================================
  Files          20       21       +1     
  Lines        2478     2475       -3     
==========================================
- Hits         2128     2123       -5     
- Misses        350      352       +2     

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