add sirus models to registry

[OkonSamuel]

continuation of #519

[codecov-commenter]

Codecov Report

Merging #524 (abac36b) into dev (e7dda4a) will not change coverage. The diff coverage is n/a.

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@@           Coverage Diff           @@
##              dev     #524   +/-   ##
=======================================
  Coverage   76.76%   76.76%           
=======================================
  Files          16       16           
  Lines        1162     1162           
=======================================
  Hits          892      892           
  Misses        270      270           

Files Changed	Coverage Δ
src/MLJModels.jl	100.00% <ø> (ø)

[rikhuijzer]

@OkonSamuel why was a new PR by the way necessary?

[OkonSamuel]

@OkonSamuel why was a new PR by the way necessary?

We added a models from SymbolicRegression.jl after you made your initial PR. I decided to open a new PR to be safe.