Support importing/pasting/dropping audio files

[humphd]

We just added support for more file types when you attach/paste/drop them. We also have support for turning audio into text, see (src/lib/speech-recognition.ts). Let's add support for importing audio files, which converts the audio to text and includes it in a new message.

[AryanK1511]

I can pick this one up. Are you able to assign it to me so I can start working on it?

[humphd]

@AryanK1511 it's all yours