Add account feature and save searches

[JackAdamsJenkins]

Fixes #4

Add user account management and search history saving functionality.

• Dependencies: Add sqlx, bcrypt, and tokio dependencies in Cargo.toml.
• Documentation: Update README.md to include instructions for setting up the database, using accounts, and saving searches.
• Command-line Arguments: Add register and login arguments in src/args.rs for user account management.
• Main Functionality: Modify src/main.rs to handle user registration, login, and search history saving.
• Data Structures: Add User and SearchHistory structs in src/data.rs for user account management and search history.
• Database Interaction: Add src/db.rs to handle database connection, user registration, login, and saving search history.