feat: onAssistantEnd handler to voice provider

[DawidWraga]

This would allow me to derive a more detailed state of the assistant.

I want to show a "waiting" indicator to the user so that they know if the assistant finished and await the response.

This could help with some of the UX issues regarding uncertainty about the assistants state.

if we could show a 'thinking' indicator too while the assistants response is loading then this would be ideal, but for now this would be a helpful first step.

[vercel[bot]]

@DawidWraga is attempting to deploy a commit to the Hume Team on Vercel.

A member of the Team first needs to authorize it.

[DawidWraga]

Relevant discord discussion with Hume support team can be found here

https://discord.com/channels/991790422433210459/1268120372054589470/1269957616206090312

[DawidWraga]

Issue has been resolved with this commit

Thank you for this @zachkrall