Add Meuse data to skgstat

[mmaelicke]

Copying the benchmark meuse dataset from https://cran.r-project.org/package=sp with correct citation hints this time,

[codecov]

Codecov Report

Merging #107 (3b810e7) into master (f9316f5) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #107      +/-   ##
==========================================
+ Coverage   91.59%   91.64%   +0.04%     
==========================================
  Files          20       20              
  Lines        2023     2035      +12     
==========================================
+ Hits         1853     1865      +12     
  Misses        170      170              

Impacted Files	Coverage Δ
skgstat/data/__init__.py	100.00% <100.00%> (ø)
skgstat/data/_loader.py	97.22% <100.00%> (+0.34%)	⬆️

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