feat: Implement Chapter 7

[danvk]

Implementation of Chapter 7: Evaluating Expressions.

[github-actions]

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[codecov]

Codecov Report

Attention: 22 lines in your changes are missing coverage. Please review.

Comparison is base (c9c1baf) 87.00% compared to head (a567301) 88.68%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/main.ts	24.00%	19 Missing ⚠️
src/interpreter.ts	98.02%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
+ Coverage   87.00%   88.68%   +1.68%     
==========================================
  Files           8        9       +1     
  Lines         554      716     +162     
  Branches       70       96      +26     
==========================================
+ Hits          482      635     +153     
- Misses         71       80       +9     
  Partials        1        1              

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