Add stable diffusion app example

[jpvotta]

Tested with

curl -X POST https://soft-smoke-dd073.apps.demo.hosted.unionai.cloud/generate \
-H "Content-Type: application/json" \
-d '{
  "prompt": "A fluffy, rust-red-colored labradoodle with straight hair and white markings smiling and panting at the camera with relaxed eyes.",
  "negative_prompt": "blurry, low quality",
  "num_inference_steps": 50,
  "guidance_scale": 10,
  "width": 512,
  "height": 512
}' \
--output my_image.png

[kumare3]

this has to be changed to parameters, please update @jpvotta