add lora demo video

Author: lucylq

program-data-separation/cpp/lora_example/README.md

@@ -237,3 +237,6 @@ I 00:00:50.189743 executorch:text_llm_runner.cpp:206] RSS after finishing text g
 ```
 
 The ExecuTorch-trained adapter model has domain knowledge of ExecuTorch codebase, whereas the Nobel-prize trained adapter model does not.
+
+## Demo video
+https://github.com/meta-pytorch/executorch-examples/tree/main/program-data-separation/cpp/lora_example/lora_demo_3.mov