Add Var::getVar

[hedtke]

This is a required pre-req. for #17

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.59%. Comparing base (3a42529) to head (1ead540).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
+ Coverage   97.53%   97.59%   +0.05%     
==========================================
  Files           9        9              
  Lines         162      166       +4     
  Branches       39       39              
==========================================
+ Hits          158      162       +4     
  Misses          3        3              
  Partials        1        1              

Files with missing lines	Coverage Δ
source/model.cpp	98.59% <100.00%> (ø)
source/var.cpp	100.00% <100.00%> (ø)