[Feature Request] Better playlist selection

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### Is your feature request related to a problem? Please describe.

The playlist feature is rather difficult to activate sometimes, especially for users that aren't incredibly technically inclined.
Loading a playlist is a separate command, the playlist title is case sensitive, and it's difficult to differentiate between different playlists in the list command.

### What is your ideal solution to the problem?

I feel that there should be a config option to have the bot check the playlist folder before searching YouTube and pull from there instead, if there's a match.

Playlist selection shouldn't be case sensitive. The titles look better capitalized in the !playlist list command, but it's confusing to invoke them with the exact same capitalization, especially if the bot owner or admins (example being myself) are inconsistent with capitalization.

I'm unfortunately not much of a developer, but as far as I understand there's already a paginator used elsewhere that could clean up !playlist list?

### How would this feature be used?

The playlist feature, while powerful, likely sees less usage because of these barriers to entry. The attached screenshots are only a couple of examples I've seen in a server with just 400 members.

Making the playlists (optionally) easier to access seems like a benefit for usability & customizability that is lacking in other music bots.

### Additional Info

Thank you for this wonderful bot!! Besides this (relatively minor) issue, our community has been loving it!

### Checklist

- [X] I have checked [the documentation](https://jmusicbot.com/) to make sure this feature doesn't already exist
- [X] I have searched for [similar feature requests](https://github.com/jagrosh/MusicBot/labels/enhancement)
- [X] I have confirmed that my requests is **not** on the [list of things that will not be added](https://jmusicbot.com/things-that-wont-be-added)
- [X] I am running the latest version of the bot: 

Start by tracing the existing !play and !playlist list command handlers, including the paginator used elsewhere. Define how local playlist matching, case-insensitive selection, and the optional configuration should interact, then verify that list output and selection work for similarly named playlists without requiring exact capitalization.

Written by the indexing model from the issue text.