Adding Grok provider

[nakul-py]

Adding new Grok provider

• As Grok does not provide free trial with API key so cannot use it without credits otherwise it works fine.

Screencast.From.2025-07-18.08-10-37.mp4

closes #126
@brichet and @jtpio

[brichet]

Thanks @nakul-py for working on this, it looks good.

I'd like someone with a credited API key to be able to test it, to make sure that everything works well before merging.

[nakul-py]

@brichet Here's a Working demo

Screencast.From.2025-08-16.09-51-56.mp4