feat: support external Hugging Face tokenizer JSON files (#1973)

examples/common/common.h

@@ -124,6 +124,7 @@ struct SDContextParams {
     std::string t5xxl_path;
     std::string llm_path;
     std::string llm_vision_path;
+    std::string tokenizer;
     std::string diffusion_model_path;
     std::string high_noise_diffusion_model_path;
     std::string uncond_diffusion_model_path;