Increase coverage & move all types/methods to root

[codecov[bot]]

Codecov Report

Merging #83 (76f6bb0) into main (245a7eb) will increase coverage by 5.59%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
+ Coverage   82.95%   88.54%   +5.59%     
==========================================
  Files          11       11              
  Lines         745      742       -3     
==========================================
+ Hits          618      657      +39     
+ Misses        127       85      -42     

Impacted Files	Coverage Δ
src/lib.rs	0.00% <ø> (ø)
src/node.rs	100.00% <ø> (+9.09%)	:arrow_up:
src/status.rs	73.68% <ø> (+36.84%)	:arrow_up:
src/model.rs	97.93% <100.00%> (+4.93%)	:arrow_up:
src/variable.rs	81.40% <100.00%> (+15.54%)	:arrow_up: