Improve README.md with clearer Quick Start and feature overview

[niveshpadamata1218]

This pull request improves the Apache SkyWalking README.md with the following enhancements:

• Added a clear and concise Quick Start section with step-by-step commands to help users get started quickly.
• Improved overview and feature descriptions for better understanding.
• Grouped and updated project badges for visual clarity.
• Clarified community contacts and code of conduct sections.
• Fixed minor formatting issues for improved readability and accessibility.

These changes aim to make the documentation more friendly and helpful to new users and contributors, facilitating adoption and contribution.

Please let me know if further refinements are needed. Thank you for reviewing!

[niveshpadamata1218]

Hi Sir,Thank you for taking the time to review my pull request. This update improves the README documentation by adding a clear Quick Start section, enhancing feature descriptions, and fixing formatting issues to make the information more accessible to new users. Please let me know if you have any feedback or suggestions—I am happy to make any necessary adjustments. Thanks again for your consideration!

[wu-sheng]

Sorry, the readme has been there for a very long time. It does not seem very reasonable to change that. Most docs are available from website.