feat: Add GEMINI_VISION_MAX_IMAGE_NUM configuration
- Introduced
GEMINI_VISION_MAX_IMAGE_NUM
to README files for better user guidance. - Updated
env.go
to retrieve the maximum image number from environment variables, defaulting to 16. - Modified image handling logic in
relay-gemini.go
to respect the new configuration, allowing disabling of the limit by setting it to -1. - Removed hardcoded constant for maximum image number in
constant.go
to streamline configuration management.