Add support to MosaicML

Implement MosaicML BaseLLMAPIClient, find out more about MosaicML API docs [here](https://docs.mosaicml.com/en/latest/inference.html#api-reference).
You can find the steps of adding BaseLLMAPIClient in the end of the [README.md](https://github.com/uripeled2/llm-client-sdk#readme)