Improve README: clearer installation steps and ADB troubleshooting for Linux

[itsaivivek]

Description

This PR improves the README.md to make the setup process much clearer and more beginner-friendly, especially for Linux users.

Main changes:

• Added explicit step-by-step instructions for enabling USB debugging on Android device
• Clarified how to download the audiosource script from releases and make it executable
• Added a dedicated Troubleshooting section for the very common "Error: adb not found" issue
  • Specifically includes solution for Linux Mint / Ubuntu-based distributions using apt
• Improved wording, flow, and structure of Installation & Usage sections
• Added note about granting microphone permission on Android

These changes should significantly reduce friction for new users trying to set up Audio Source, especially those running into ADB-related problems.

Related issues

None (preventive improvement)

Testing

• Verified the written steps work on Linux Mint
• Instructions match current release assets structure

Thank you for considering this contribution!

[gdzx]

Hi!

Thanks for your PR. There are some formatting issues such as hard line breaks so I cannot merge it as-is, but I copied most of the changes in next.

Best regards