Implement commands for CLI

[worthant]

Proposed Commands for HandyDB

• set <key> <value>: Sets or updates a value for a given key.
• get <key>: Retrieves the value associated with a given key.
• add <key> <value>: Adds a new key-value pair, errors if key exists.
• append <value>: Appends a value with an auto-generated key.
• delete <key>: Deletes a key-value pair based on the key.
• exists <key>: Checks if a key exists in the database.
• list or keys: Lists all keys in the database.
• clear: Clears all data from the database.
• update <key> <value>: Updates the value for an existing key, errors if key doesn't exist.
• info: Displays information about the database.
• help: Displays help information about commands.
• exit or quit: Exits the database CLI.
• export <filename>: Exports database contents to a file.
• import <filename>: Imports data from a file into the database.
• find <pattern>: Searches for keys matching a pattern.
• history: Shows a history of executed commands (optional).
• stats: Shows statistics about database usage and performance.
• rename <old_key> <new_key>: Renames a key.
• merge <key1> <key2> <new_key>: Merges two keys into a new key.

[worthant]

[worthant]