feat: Add AST, AST visitor, printer test

[danvk]

Overview

Implements AST from Chapter 5 of Crafting Interpreters.

This chapter is almost entirely Java-isms, so the TS version looks quite different. I'm actually very happy with it! Interfaces, tagged unions and mapped types are quite nice for reducing boilerplate here.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (dbcd077) 87.61% compared to head (5e53ce1) 88.79%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #7      +/-   ##
==========================================
+ Coverage   87.61%   88.79%   +1.18%     
==========================================
  Files           5        6       +1     
  Lines         331      366      +35     
  Branches       48       48              
==========================================
+ Hits          290      325      +35     
  Misses         40       40              
  Partials        1        1              

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