Add unit test for meanvote and postprocess

[felixcremer]

This adds unit tests for meanvote and post process via the example data.
This also changes the default threshold to reflect the classification.

I also added a classify keyword to rqatrend so that we can run the raw rqatrend without the classifcation. This was mainly used to understand and verify whether the classify is working as expected.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.18%. Comparing base (28e0223) to head (71a80c9).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rqatrend.jl	85.71%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #125       +/-   ##
===========================================
+ Coverage   66.55%   81.18%   +14.63%     
===========================================
  Files           6        6               
  Lines         287      303       +16     
===========================================
+ Hits          191      246       +55     
+ Misses         96       57       -39     

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