🤖 Add option to use GPT-4

[a-n-d-a-i]

Many of your users have access to GPT-4 already. I checked the settings but there is no option to use it. I checked the code, and the model name is baked-in as gpt-3.5-turbo. It would be very nice to have a GPT-4 option considering the difference in quality. (Might be worth adding a notice that using GPT-4 will be slower and more expensive.)

[OVAWARE]

I would agree. Allow users to choose between GPT-3.5, 3 and 4 when they have there custom token.

[gauravsaini]

https://github.com/reworkd/AgentGPT/pull/39

[asim-shrestha]

Thanks @gauravsaini that will help on the dev side, for production usage @Jshen123 is working on something

[Jshen123]

PR (#88) for issue #33

[APiTJLillo]

Model input has been added in settings