Spring-ai Add OllamaClient implementation of AiClient

Hi, I just implemented the Ollama LLM client. Can someone review it?

Comment From: markpollack

will make changes on merge. Thanks for the PR. If you can, creating the starter would be much appreciated - https://github.com/spring-projects-experimental/spring-ai/issues/68

Comment From: markpollack

Merged as e68bdeb9a0d74badacaccc1677521fd2612f5b71