Support for Google Gemini

Hi!

Thank you for such a great extension and all the contributions that have been added to this project.

I wonder if there is a plan to add support for Google Gemini into the tool?

If no, do we think there is some additional help needed to add it and externally produced changes can be accepted into the mainline branch?

Thanks again!

此 issue 未指定任何檔案、測試或進入點，除了新增 Google Gemini 支援之外，也沒有提供其他驗收標準。請先檢視現有的 OpenAI-compatible、Tabby 和 Ollama 整合；當 Gemini 支援完成整合並驗證其預期行為後，工作即告完成，但這些細節在此未有指定。

由索引模型根據 Issue 內容生成。