Improved the Taproot documentation with better description and organisation

[JAGADISHSUNILPEDNEKAR]

Improved Taproot Documentation in README

This PR enhances the Taproot section of the README by:

1. Adding a clear, concise introduction to Taproot that explains its key benefits (privacy, efficiency, and smart contract capabilities)
2. Organizing the Taproot examples into logical sections based on functionality:
   • Basic key path spending
   • Single script path examples
   • Multiple script paths examples
3. Improving the descriptions of each example to better explain what they demonstrate

These changes make the Taproot functionality more approachable for new users, help developers understand which examples to look at based on their needs, and highlight the comprehensive Taproot support in the library.

No code changes were made - this is purely a documentation improvement.