[Docs] Add a note on SDEdit (#2433)

add: note on SDEdit

docs/source/en/api/pipelines/stable_diffusion/img2img.mdx

@@ -20,6 +20,9 @@ The original codebase can be found here: [CampVis/stable-diffusion](https://gith
 
 [`StableDiffusionImg2ImgPipeline`] is compatible with all Stable Diffusion checkpoints for [Text-to-Image](./text2img) 
 
+The pipeline uses the diffusion-denoising mechanism proposed by SDEdit ([SDEdit: Guided Image Synthesis and Editing with Stochastic Differential Equations](https://arxiv.org/abs/2108.01073)
+proposed by Chenlin Meng, Yutong He, Yang Song, Jiaming Song, Jiajun Wu, Jun-Yan Zhu, Stefano Ermon).
+
 [[autodoc]] StableDiffusionImg2ImgPipeline
 	- all
 	- __call__