Command to assign roles

**Feature request:**
I would like to implement adding roles to users with the bot, so I could do something like ?add_role Member instead of having to open up their profile and change the role

**Describe alternatives you've considered**
Maybe allow the bot to give roles based on the reaction selected and also take them away when a person unselects the reaction

Look for command handling code, likely in a cogs or commands directory, to see how existing bot commands are structured. Check Discord.py documentation for role management APIs. Implement a new command that parses user and role arguments, then adds the role. Test by running the bot and verifying role assignment works.

Scritto dal modello di indicizzazione a partire dal testo della issue.