Adding Litellm client and some models/providers.

[OSH212]

Description

Created litellm_client.py for LiteLLM and updated llm.py, sample.config.toml and README.md accordingly. I tested it with OpenRouter and DeepInfra hosted models.

Explain what existing problem does the pull request solve?

Allowing usage of LiteLLM framework

Test plan (required)

Demonstrate the code is solid. Example: The exact commands you ran and their output, screenshots / videos if the pull request changes UI.

24.05.15 17:05:02: root: INFO : User message: {'message': 'create a modern snake game', 'base_model': 'OpenRouter: Gemma 7B', 'project_name': 'gemma', 'search_engine': 'Google'} 24.05.15 17:05:02: root: INFO : SOCKET server-message MESSAGE: {'messages': {'from_devika': False, 'message': 'create a modern snake game', 'timestamp': '2024-05-15 17:05:02'}} 24.05.15 17:05:02: root: INFO : SOCKET agent-state MESSAGE: [{'internal_monologue': "I'm starting the work...", 'browser_session': {'url': None, 'screenshot': None}, 'terminal_session': {'command': None, 'output': None, 'title': None}, 'step': 1, 'message': None, 'completed': False, 'agent_is_active': True, 'token_usage': 0, 'timestamp': '2024-05-15 17:05:02'}] 24.05.15 17:05:02: root: INFO : SOCKET tokens MESSAGE: {'token_usage': 734}

Closing issues (optional)

Fixes #