add groq as model provider

[warengonzaga]

We would like to add Groq as one of the model providers. This one requires its prompt.

Reference: https://console.groq.com/docs/api-reference#chat-create

If anyone wants to add this, feel free to let me know. Remember to read the contributing file from the repository's root. If you have questions about this feature request please tag me.

[warengonzaga]

We can use Groq as the default model if no API key is provided.