Add image-to-image pipeline tag

This PR adds the `image-to-image` pipeline tag to the model card metadata, improving discoverability of this model. The model performs image editing based on text instructions, making this tag highly relevant.

README.md

@@ -1,5 +1,9 @@
 ---
 base_model: timbrooks/instruct-pix2pix
+datasets:
+- SherryXTChen/InstructCLIP-InstructPix2Pix-Data
+language:
+- en
 library_name: diffusers
 license: apache-2.0
 tags:
@@ -9,10 +13,7 @@ tags:
 - diffusers
 - diffusers-training
 inference: true
-datasets:
-- SherryXTChen/InstructCLIP-InstructPix2Pix-Data
-language:
-- en
+pipeline_tag: image-to-image
 ---
 
 # InstructCLIP: Improving Instruction-Guided Image Editing with Automated Data Refinement Using Contrastive Learning