Add support for mistral AI api keys

[julian-st]

Add support for mistral AI api keys
see the following documentions for python
https://docs.mistral.ai/getting-started/quickstart/

i propose the environment variable name
MISTRAL_API_KEYS
if both MISTRAL_API_KEYS and GEMINI_API_KEYS are given use gemini as default
if only one api key is given use only that one

[sammcj]

May I make a suggestion here and instead simply support and LiteLLM provider and model.

e.g. ollama/qwen3:14b, anthropic/claude-sonnet-4-latest

[simedw]

I'm adding LiteLLM support here #11 , should be merged in and released in a day or two

[simedw]

Just released it, let me know if it works for you.

[simedw]

I'm closing this for now, but if you have any issues with using mistral feel free to open.