FEAT add beam search

[MatthewSZhang]

Checklist

• Used a personal fork to propose changes
• A reference to a related issue: FEAT beam search #41
• A description of the changes: add beam search for FastCan

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e47b6fa) to head (359e824).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #187   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9        10    +1     
  Lines          611       685   +74     
=========================================
+ Hits           611       685   +74     

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