Chatbot Arena: Add phi-2 and phi-3 models

[EwoutH]

The Phi-3 Technical Report was just published by the Microsoft team, in which they introduce a model family of 3 state-of-the-art models:

• phi-3-mini (3.3B)
• phi-3-small (7B)
• phi-3-medium (14B)

Phi-3 weights are not yet available, but to have a good baseline, it might be interesting to also add phi-2 support.

[EwoutH]

Phi-3-mini weights are released: https://huggingface.co/collections/microsoft/phi-3-6626e15e9585a200d2d761e3

[EwoutH]

They are added on https://chat.lmsys.org/ so I'm closing this issue as completed.