Add --json output format

[scooke11]

/bounty 50

Problem

Currently the CLI only outputs human-readable text. We need JSON output for scripting and automation.

Requirements

• Add --json flag to all commands (add, list, done)
• Output valid JSON when flag is present
• Include tests for JSON output format
• Update README with JSON output examples

Acceptance Criteria

• All commands support --json flag
• JSON output is valid and parseable
• Tests pass with new functionality
• Documentation updated with examples

[Brijeshthummar02]

@scooke11 can i work on bounty?

[EugeneJarvis88]

I'd like to work on this bounty. I have already implemented the solution locally:

Changes made:

• Added global --json flag to main parser
• Updated add_task(), list_tasks(), mark_done() to support return_data=True
• Added comprehensive tests (8 tests, all passing)
• Updated README with JSON output examples

Sample output:

{
  "success": true,
  "message": "Added task 1: Buy groceries",
  "task": {"id": 1, "description": "Buy groceries", "done": false}
}

Will submit PR once I can fork the repository.

[thecafetron-ctrl]

/attempt #1

Plan:

• Add a global --json flag to CLI.
• When enabled, return machine-readable JSON for add/list/done commands (consistent envelope: success, message, data).
• Add tests verifying JSON is parseable and matches expected structure.
• Update README with --json usage examples.