update jumpIn and jumpIn`

[mrufrufin]

Newcomer from the Tidal issue before. I've noticed the documentation for thejumpIns missing (and out-of-date in the repo) so here's my attempt at documentation for those (apologies for newbie errors). Not sure if this is the right place to contribute to the documentation (it seems like tidalcycles.org and this repo are a bit out-of-sync?).

Not sure if these are a bit too wordy, I've tried to put stuff down that somewhat trace my thought processes getting my head around these...