Add RR Lyrae test dataset

[hombit]

No description provided.

[codecov]

Codecov Report

Patch coverage: 84.05% and project coverage change: -0.71% ⚠️

Comparison is base (038612a) 93.64% compared to head (8f39781) 92.93%.
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #127      +/-   ##
==========================================
- Coverage   93.64%   92.93%   -0.71%     
==========================================
  Files          76       77       +1     
  Lines        6796     6939     +143     
==========================================
+ Hits         6364     6449      +85     
- Misses        432      490      +58     

Files Changed	Coverage Δ
src/time_series.rs	93.46% <ø> (-0.99%)	⬇️
test-util/src/lc_data/from_issues.rs	59.09% <50.94%> (-39.19%)	⬇️
test-util/src/lc_data/record.rs	47.36% <80.00%> (-39.00%)	⬇️
test-util/src/lc_data/types.rs	94.82% <94.73%> (-5.18%)	⬇️
src/features/bazin_fit.rs	98.33% <100.00%> (-0.01%)	⬇️
src/features/eta_e.rs	100.00% <100.00%> (ø)
src/features/linear_trend.rs	100.00% <100.00%> (ø)
src/features/otsu_split.rs	91.19% <100.00%> (ø)
src/features/villar_fit.rs	98.58% <100.00%> (ø)
src/tests.rs	88.85% <100.00%> (+0.27%)	⬆️
... and 3 more

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