style: standardize markdown formatting in README

Improve consistency and readability by:
- Normalize list indentation from 4 to 2 spaces
- Use hyphens instead of asterisks for list markers
- Standardize italic syntax using underscores
- Add consistent spacing between sections

These formatting changes follow common Markdown conventions without
altering any content.

🤖 Generated with Claude Code (https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

Author: vinta