Added functionality to turn playlist link -> array of individual youtube links

[nednoodlehead]

Only exists for the blocking version. I do not know how to do the async version.

Also I did not add any interface within the repo to interact with it, I figured that would be best done by a maintainer.

[DzenanJupic]

Hey, @nednoodlehead thanks for your work. Looks good at first sight, I'll have a deeper look at it this weekend.

[nednoodlehead]

Alright, I also can't seem to expose the file to the rest of the crate. I added a pub mod playlist; inside of the mod.rs file, but it seems to not change much, as I keep getting the unresolved import rustube::blocking::playlist