docs: document useNFTData and useMintNFT hooks (#33)

[cryptoflops]

Summary

This PR adds comprehensive documentation for the NFT hooks in Composer Kit, addressing issue #33.

Changes Made

• Updated: apps/docs/docs/pages/components/nft/nft-mint.mdx

Added Documentation For:

1. useMintNFT Hook

   • Overview and purpose
   • Parameters table
   • Return value properties
   • MintParams interface
   • Complete usage example

2. useNFTData Hook

   • Overview and purpose
   • Parameters with types
   • Return value properties
   • NFTMetadata interface
   • Complete usage example with metadata rendering

3. Props Section for NFTMint component

Related Issue

Closes #33

Testing

• Verified documentation follows existing Vocs/MDX patterns
• Code examples are syntactically correct
• All hook parameters and return values match actual implementation

Checklist

• I have read the Code Contributors guidelines
• This is a focused, single-purpose change
• Documentation matches the actual hook implementations