Add reference_attn & reference_adain support for sdxl (#4502)

* ADD SDXL reference & reference adain

* Update README.md

* Update README.md

* format stable_diffusion_xl_reference.py

* format file

* Format file

* format file

* fix format

* fix format with ruff

* fix format

* Update examples/community/README.md
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

* Update examples/community/README.md
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

* Update README.md

* Update README.md & fix typo

* Update README.md

* fix format

---------
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

examples/community/README.md

@@ -1889,3 +1889,69 @@ for obj in range(bs):
 
 ```
 
+### Stable Diffusion XL Reference
+
+This pipeline uses the Reference . Refer to the [stable_diffusion_reference](https://github.com/huggingface/diffusers/blob/main/examples/community/README.md#stable-diffusion-reference).
+
+
+```py
+import torch
+from PIL import Image
+from diffusers.utils import load_image
+from diffusers import DiffusionPipeline
+from diffusers.schedulers import UniPCMultistepScheduler
+input_image = load_image("https://hf.co/datasets/huggingface/documentation-images/resolve/main/diffusers/input_image_vermeer.png")
+
+# pipe = DiffusionPipeline.from_pretrained(
+#     "stabilityai/stable-diffusion-xl-base-1.0",
+#     custom_pipeline="stable_diffusion_xl_reference",
+#     torch_dtype=torch.float16,
+#     use_safetensors=True,
+#     variant="fp16").to('cuda:0')
+
+pipe = StableDiffusionXLReferencePipeline.from_pretrained(
+    "stabilityai/stable-diffusion-xl-base-1.0",
+    torch_dtype=torch.float16,
+    use_safetensors=True,
+    variant="fp16").to('cuda:0')
+
+pipe.scheduler = UniPCMultistepScheduler.from_config(pipe.scheduler.config)
+
+result_img = pipe(ref_image=input_image,
+      prompt="1girl",
+      num_inference_steps=20,
+      reference_attn=True,
+      reference_adain=True).images[0]
+```
+
+Reference Image
+
+![reference_image](https://hf.co/datasets/huggingface/documentation-images/resolve/main/diffusers/input_image_vermeer.png)
+
+Output Image   
+
+`prompt: 1 girl`
+
+`reference_attn=True, reference_adain=True, num_inference_steps=20`
+![Output_image](https://github.com/zideliu/diffusers/assets/34944964/743848da-a215-48f9-ae39-b5e2ae49fb13)
+
+Reference Image
+![reference_image](https://github.com/huggingface/diffusers/assets/34944964/449bdab6-e744-4fb2-9620-d4068d9a741b)
+
+
+Output Image 
+
+`prompt: A dog`
+
+`reference_attn=True, reference_adain=False, num_inference_steps=20`
+![Output_image](https://github.com/huggingface/diffusers/assets/34944964/fff2f16f-6e91-434b-abcc-5259d866c31e)
+
+Reference Image
+![reference_image](https://github.com/huggingface/diffusers/assets/34944964/077ed4fe-2991-4b79-99a1-009f056227d1)
+
+Output Image
+
+`prompt: An astronaut riding a lion`
+
+`reference_attn=True, reference_adain=True, num_inference_steps=20`
+![output_image](https://github.com/huggingface/diffusers/assets/34944964/9b2f1aca-886f-49c3-89ec-d2031c8e3670)
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