feat: add configurable reference image processing for edit models (#1780)

examples/common/common.h

@@ -227,6 +227,8 @@ struct SDGenerationParams {
     sd_tiling_params_t vae_tiling_params = {false, false, 0, 0, 0.5f, 0.0f, 0.0f, nullptr};
     std::string extra_tiling_args;
 
+    std::string ref_image_args;
+
     std::string pm_id_images_dir;
     std::string pm_id_embed_path;
     float pm_style_strength = 20.f;