Add truffleruby in CI

[eregon]

Found #115 but didn't look further, is it OK to add?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (d3c075c) to head (d818e19).
⚠️ Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #130   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines           90        90           
=========================================
  Hits            90        90           

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