add function mkplaylist()

[tatsumoto-ren]

solves #11

[Daja177]

In this PR's current state there isn't anything using this function, and no option to use it instead of reshuffle() when running impd reshuffle or impd rotate. Is this something you plan on making possible eventually, for example through a config parameter?

[tatsumoto-ren]

Yes, this is a standalone function. It can be used by running impd mkplaylist.

[tatsumoto-ren]

Is this something you plan on making possible eventually, for example through a config parameter?

I think this can be added in a next PR. I'm looking forward to PRs from people like you who actually need this feature.