Update unexported-airnode-features

[metobom]

Pusher uses an old version of processing for pre/post-processing under unexported-airnode-features folder. We need this feature from Airnode 0.12.0.

Possibly related to #77

[bbenligiray]

@Siegrift we can just do this to avoid having the v0.1 release be blocked by #77

[Siegrift]

I can finish api3dao/commons#9 which we can then release and then merge #75.

I think we can do the above tomorrow, so that should be fine?

[bdrhn9]

Fwiw, in the concept implementation I created this pre/post functions externally not for they are unexported but to implement requested feature. It's here paremeters are also passed to post-processing (current one here). So, the example config generated by Nodary won't work because we are leveraging parameters in post processing, see https://github.com/api3dao/signed-api/blob/main/packages/pusher/config/pusher.example.json#L82.

[Siegrift]

Yeah, but this was later already implemented in Airnode. You can see that the pusher config the same as the Nodary one and I checked that it works.