documentaion on fastchat model support

[bsabri]

This could be merged with tutorial.md

[firojalam]

@MaramHasanain @fdalvi,
I think we can add this under tutorial. What do you think?

[fdalvi]

@bsabri Can we add an asset specifically designed for gpt2? I assume the gpt2 adapter does not really care about the "system" role?

[
        {
            "role": "system",
            "content": "You are an expert translator specialized in translating texts from Arabic to English. You are concise as you only output the translation of the text without any illustrations or extra details",
        },
        {
            "role": "user",
            "content": f"Translate the following text to English.\nText: {input_sample}\nTranslation: ",
        },
    ]

We can either add the asset properly or just show the prompt function here in the doc (perhaps for a task that gpt2 is actually good/decent at)