Improve docs: quickstart guide, standardize README, add results table

[rajkumar42]

Summary

Make this benchmark repo more accessible to new contributors by adding a quickstart guide, standardizing the README structure, and including a results summary table.

What needs to happen

Quickstart ("Run your first benchmark in 5 minutes")

• Add a short section at the top of README with minimal steps to run the benchmark
• Include: clone, install deps, set API key, run a small subset
• Example: python run_benchmark.py --limit 5 to run just 5 tasks

Standardize README

• Follow a consistent structure: Overview → Quickstart → Full Setup → Results → Contributing
• Align with other OpenSymbolicAI benchmark repos for consistency
• Include badges (Python version, license, etc.)

Results summary table

• Add a markdown table showing results per model/provider
• Columns: Model | Pass Rate | Avg Tokens | Avg Cost | Date
• Keep the table updated as new provider results come in

Acceptance criteria

• A newcomer can go from clone to first benchmark result in under 5 minutes
• README follows the standardized structure
• Results table is present with at least one row of data