[Feature Request] AutoDJ

**Is your feature request related to a problem? Please describe.**
No. It's just an enchantment.

**Describe the solution you'd like**
I would like to see an auto DJ, that will automatically play songs, based on the genre u used on the command.

**Describe the basic flow/steps of using this feature**
How this feature would be used:
1. Option on the config to enable dj [true-false]
2. If it is true, any user with the DJ role can do `autodj [music genre]`
3. The bot starts playing music that is based in the music genre the user has specified
4. If the user writes autodj off, the bot stops playing music in this mode, and it returns to the default mode.

**Have you confirmed that this idea is not already described here?**
https://github.com/jagrosh/MusicBot/projects/1: Yes

Start by locating the bot’s existing configuration, DJ-role permission handling, command entry points, and music playback flow. Define the behavior for the `autodj [music genre]` and `autodj off` commands, including the config toggle; done means eligible users can start and stop genre-based playback while normal playback remains available.

Written by the indexing model from the issue text.