docs: Add CLI commands to README

[ZaidQtaish]

Description

Adds a new "Commands" section to the Usage section in the README that documents all available CLI commands including:

• git-scope - Launch TUI dashboard
• git-scope init - Create config file interactively
• git-scope scan - Scan and print repos (JSON)
• git-scope scan-all - Full system scan from home directory
• git-scope issue - Open GitHub issues page in browser
• git-scope -h - Show help

This makes it easier for new users to discover all available commands without running the help flag.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• [] ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)

Checklist

• I have tested my changes locally
• I have updated the documentation (if applicable)
• My code follows the project's style guidelines
• I have added tests that prove my fix/feature works (if applicable)

Screenshots (if applicable)