Add CSON (CoffeeScript Object Notation) codec

[Copilot]

This PR implements a complete CSON (CoffeeScript Object Notation) codec for the json-pack library, adding support for a human-readable alternative to JSON with enhanced syntax features.

What is CSON?

CSON is CoffeeScript Object Notation - a more flexible and readable format than JSON that supports:

• Comments: Single-line (#) and multi-line (###) comments
• Unquoted keys: Valid identifiers don't need quotes
• Flexible arrays: Elements can be written without commas
• Multi-line strings: Triple-quoted strings (''')
• Trailing commas: Optional in most contexts

Implementation

CsonEncoder

• Converts JavaScript objects to human-readable CSON format
• Supports all standard data types: null, boolean, number, string, array, object, binary data
• Automatically quotes invalid identifier keys while leaving valid ones unquoted
• Configurable indentation and formatting options
• Uses existing @jsonjoy.com/base64 utilities for binary data encoding

CsonDecoder

• Parses CSON text back to JavaScript objects
• Leverages the battle-tested cson-parser library for robust parsing
• Handles all CSON-specific syntax features including comments and multi-line strings
• Provides clear error messages for invalid CSON

Example Usage

import {Writer} from '@jsonjoy.com/util/lib/buffers/Writer';
import {CsonEncoder, CsonDecoder} from '@jsonjoy.com/json-pack/lib/cson';

const writer = new Writer();
const encoder = new CsonEncoder(writer);
const decoder = new CsonDecoder();

const data = {
  name: 'my-app',
  features: ['logging', 'monitoring', 'caching'],
  config: { debug: true, timeout: 5000 }
};

// Encode to CSON
const encoded = encoder.encode(data);
console.log(new TextDecoder().decode(encoded));
// Output:
// name: 'my-app'
// features: [
//   'logging'
//   'monitoring' 
//   'caching'
// ]
// config: {
//   debug: true
//   timeout: 5000
// }

// Decode back to JavaScript
const decoded = decoder.decode(encoded);
// Perfect round-trip: decoded === data

Testing

• 46 comprehensive tests covering encoder, decoder, integration, and edge cases
• Full roundtrip compatibility validation
• Support for complex nested structures
• Error handling for malformed CSON
• All existing tests continue to pass (2775 total tests)

Documentation

• Complete README with usage examples and feature documentation
• Integration examples showing CSON-specific features
• Updated main README to include CSON in supported formats
• Working demo script demonstrating encoding/decoding capabilities

Dependencies

• Added cson-parser for robust CSON parsing (minimal footprint)
• No breaking changes to existing APIs
• Follows established library patterns and interfaces

The CSON codec provides an excellent option for configuration files and human-editable data while maintaining json-pack's performance standards.

Fixes #23.

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[streamich]

Run linter and formatter when you are done.

[streamich]

Do not use cson-parser implement the parsing from scratch.

[Copilot]

I've implemented a complete CSON parser from scratch without using the cson-parser library. The new implementation supports all CSON features including comments, unquoted keys, flexible arrays, multi-line strings, and indentation-based nested objects. All 46 existing tests continue to pass. The dependency has been removed from package.json. (commit b0ab0bc)

[Copilot]

Run linter and formatter when you are done.

I've run both the linter and formatter on the codebase. All linting errors in the new CSON code have been fixed and the code has been properly formatted using Prettier. (commit b0ab0bc)

[streamich]

Run formatter and linter when done.

[streamich]

1. Do not create a seprate CsonParser class, parse in CsonDecoder class. Decoder is our parser.
2. You have to parse from Uint8Array (use Reader), not string. See how it is done in JsonDecoder and other codecs in this repo.

[Copilot]

I've implemented both requested changes:

1. Removed separate CsonParser class - All parsing logic is now directly integrated into the CsonDecoder class, following the same pattern as other decoders in the repository.

2. Parse from Uint8Array using Reader - The decoder now parses directly from bytes using the Reader class, eliminating the string conversion step. The implementation follows the same byte-level parsing approach as JsonDecoder with methods like readValue(), readString(), readNumber(), etc.

All 46 CSON tests continue to pass, and the full test suite (2775 tests) also passes. The refactor maintains all CSON features while improving performance through direct byte parsing.

(commit a16308b)

[Copilot]

Run formatter and linter when done.

Linter and formatter have been run successfully. The linter completed without any issues in the CSON code, and the formatter showed all files as "unchanged" indicating the code was already properly formatted. All 2775 tests continue to pass. (commit a16308b)