sub-skip update readme

[mrfragger]

perhaps this was the old way..not sure when it changed

Ctrl+n: activate skipping (toggle)
Ctrl+Alt+n: toggle between speedup and seek skip (switch-mode)

should be

Ctrl+n: Non-Subtitle skip (toggle)
Ctrl+Alt+n: Seek skip to next sub (toggle)

also edit
script-binding sub-pause/-replay; script-binding sub-pause-skip-next

should be

script-binding sub_pause/replay; script-binding sub_pause/skip-next