docs: Add comprehensive contract deployment and update guide

[crStiv]

This PR addresses issue #2409 (part of #2407) by adding detailed documentation for contract deployment and updates.

Changes:

• Created new document doc/contract-deployment.md
• Added step-by-step instructions for:
  • Local testnet deployment
  • Sepolia testnet deployment
  • Contract update process
  • Gas profiling guidelines
• Included important notes and best practices

This documentation will help developers better understand the contract deployment process and maintain consistency in contract updates.

[crStiv]

@sveitser sorry for disturbing, just wanna make sure you seethis pr