Add Llama2 and NoowAi Provider

[hlohaus]

No description provided.

[yicone]

Awesome! Thanks for your work!

When trying to access llama2 provider, I encountered several issues：

1. the model name of "70B" not defined in './models.py'.
   File "/Users/tr/Library/CloudStorage/Dropbox/Workspace/HandsOnLabs/gpt4free-playground/.venv/lib/python3.11/site-packages/g4f/__init__.py", line 33, in get_model_and_provider raise ValueError(f'The model: {model} does not exist') ValueError: The model: 70B does not exist
2. When trying to access llama2, encountered several issues：
   aiohttp.client_exceptions.ClientConnectorError: Cannot connect to host www.llama2.ai:443 ssl:default [Connect call failed ('50.117.117.42', 443)]
   I tried to ask a question on https://www.llama2.ai, but I did not receive any response. The network request did not receive any response content. I am unsure if the service has been stopped.