Drop dependencies

[vwmaus]

• Replaces spatial data handling with sf and stars
• Uses TWDTW from twdtw CRAN package
• Adds 1NN-TWDTW train function
• Adds model class with support for stars::predict
• Adds documentation
• Adds tests
• Adds stars vignette
• Changes array input mode to 3D
• Pretty model print

[codecov]

Codecov Report

Merging #60 (d2f9c56) into master (1eb27b5) will increase coverage by 2.00%.
The diff coverage is 88.81%.

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
+ Coverage   87.32%   89.33%   +2.00%     
==========================================
  Files           3        5       +2     
  Lines          71      150      +79     
==========================================
+ Hits           62      134      +72     
- Misses          9       16       +7     

Files Changed	Coverage Δ
R/prepare_time_series.R	83.78% <83.78%> (ø)
R/train.R	87.80% <87.80%> (ø)
R/plot.R	100.00% <100.00%> (ø)
R/predict.R	100.00% <100.00%> (ø)
R/shift_dates.R	100.00% <100.00%> (ø)