Suggestion: `next_search` action

[maverickwoo]

As of the current master a27e7df, we have C-r bound to prev_search by default. However, there is no opposite action to this. May I suggest adding the opposite action next-search and bind it to C-s by default? This can be very handy when undoing a reverse search that went some step(s) too far.

Thank you for your consideration.

Indeed, I'll have a look