PromptInputSpeechButton : Make speech recognition language configurable

[amaryassa]

Currently, the speech recognition language is hardcoded:

// prompt-input.tsx
speechRecognition.lang = "en-US";

Passing a lang prop does not work:

<PromptInputSpeechButton
  onTranscriptionChange={setInput}
  textareaRef={textareaRef}
  lang="fr"
/>

Proposed fix

Add a lang props to PromptInputSpeechButton:

speechRecognition.lang = "en-US" lang;

// prompt-input.tsx
export const PromptInputSpeechButton = ({
  className,
  textareaRef,
  onTranscriptionChange,
  lang = "en-US",
  ...props
}) => {...}