Challenge: Add an Instruction

Time to modify the program. Add a greet instruction that logs a greeting message.

Requirements

1. Add a new function greet inside the #[program] module
2. It should take _ctx: Context<Greet> as its parameter
3. It should call msg!("Hello, Solana!") and return Ok(())
4. Add a corresponding Greet accounts struct (can be empty, like Initialize)

Tips

• Follow the same pattern as the existing initialize function
• The accounts struct name must match the Context<T> generic
• Don't forget #[derive(Accounts)] on your new struct