Mandelbrot benchmark and chained Negatives doc

[Valent-p]

Summary of Changes for Pull Request

1. Documented Chained Logical NOT (!) Operator in Lox

• Added an explanation and examples demonstrating that Lox supports chaining the logical NOT operator.
• Clarified that expressions such as !!!!true and !!!false are valid in Lox and how they evaluate.
• Provided sample code to illustrate this behavior:

  print !!!!true;  // prints true
  print !!!false;  // prints true
  print !!false;   // prints false
  

2. Added Mandelbrot Benchmark

• Created a new benchmark file: test/benchmark/mandelbrot.lox.
• This benchmark implements the Mandelbrot set calculation and prints the result as ASCII art.
• The benchmark can be used to evaluate the performance of the Lox interpreter on computationally intensive code.

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These changes improve the documentation for Lox’s logical operators and expand the benchmark suite with a classic numerical benchmark.