Delays not being applied

[Rich-Harris]

Think I just forgot to implement this (REPL).

It does raise a question though — if a bidirectional transition has a delay, should it apply if a transition is aborted, or only for fresh transitions? I.e. if you reverse an intro half-way through, should you wait half a second before outroing, or outro immediately? I guess it would be surprising if the delay wasn't applied, in which case presumably we can't abort the intro until the outro starts.

Any thoughts? (This is the sort of thing I meant when I said I wanted to avoid opinions as far as possible, but sometimes you can't avoid the need to have some...)