[Feature Request] repeat specific length on a song

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

- Repeat a whole song is already implemented (!repeat). But currently, it's not possible to repeat specific length of a song. (e.x. repeat 2:00-3:15 of a song)

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

- add the feature so we can specify a length of song to loop. like !repeat 2:00-3:15

### How would this feature be used?

1 add/play a song
2 execute the command like above.
3 specified part of a song will repeat over and over and over

### Additional Info

English is not my first language, so if you have any questions or needs clarification, feel free to ask me about 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 locating the existing !repeat command and the song playback or queue handling it uses. Determine how a time range such as 2:00-3:15 can be parsed and looped, then verify that the specified segment repeats continuously without changing whole-song repeat behavior.

Written by the indexing model from the issue text.