JSON Parser & Benchmark

## About JSON Parser The **PetitParser JSON grammar** implements the [ECMA-404 JSON standard](https://www.json.org/) directly as composable Dart parser combinators. ### Key Parser Features - **Grammar Structure**: Defined using modular rules for objects, arrays, strings with escape sequences, numbers, and boolean/null tokens. - **Pure Dart Execution**: Operates entirely within Dart bytecode or WebAssembly, enabling runtime inspection, debugging, and AST customization. - **Extensible Grammar**: Can serve as a template to support custom variants such as JSON5, JSON with comments (JSONC), trailing commas, or alternative number formats. - **Comparative Benchmark**: Includes a live side-by-side benchmark comparing combinator parsing against platform-native `dart:convert`.