Feature Request: Support writing individual media segment to string

[TheKeveloper]

Hello! Not sure if this is already possible (I couldn't find how to do this), but I'm interested in getting the string representation of individual media segments instead of the entire playlist.

The reason is that we maintain an HLS server where we append segments to a playlist on disk as we construct new media segments, and it would be nice if we could use the m3u8-parser logic to generate the string representation instead of either having to parse the existing playlist or try to construct the string representation externally.

I'm happy to put up a PR for this, but wanted to check if this generally seems like a sensible addition?

Thank you!