Add Whisper Prompt option to API call

[CaiCharley]

Would you be able to add an option to set a prompt for the whisper API call as Whisper continuously misspells some words for me and exposing the prompt option would be really useful to set spellings of certain words. I think it could be as simple as adding a formData.append('prompt', userPrompt); to your whisper.ts file and exposing it through the UI similar to how you implement setting an API key.

Thanks.

[doxgt]

This may be a duplicate from #85. I second that anyway.

However, take a look here: https://github.com/braden-w/whispering/issues/51#issuecomment-2119316375