0.29.0

Please run Copilot for Xcode.app once and restart Xcode to complete the update.

• Add support for Google Gemini as a chat model.
• Supports files with different line endings like \r and \r\n. #404
• Supports extensions built with CopilotForXcodeKit.
• Improve prompts of prompt to code.
• Improve behavior of chat when it tries to read the code at specific line.
• Other small fixes.