Docs: Update README with troubleshooting and full details

[Amansarfraz]

This pull request updates the README.md for the Dev Cleaner Utility.

Changes included:

• Added a poster and badges for visual clarity
• Detailed Features section with Flutter, Xcode, Visual Studio, Gradle, npm, NuGet, IDE cleanup
• Installation instructions for Linux/macOS (direct script & Homebrew) and Windows (PowerShell)
• Command-line options and environment variables documented
• Windows-specific cleanup explained
• Detailed Flutter cleanup instructions
• Added Troubleshooting / Common Issues section covering permission, PATH, Brew, PowerShell, and admin issues
• Contribution and support sections updated

Purpose:

Improves onboarding, provides full guidance for users on multi-platform cleanup, and solves documentation gaps.

Closes #29

[jemishavasoya]

@Amansarfraz

Please look into it.

Thanks!!!!