Add metadata tags

This PR ensures the model can be found at https://huggingface.co/models?pipeline_tag=image-to-image&sort=trending

README.md

@@ -1,5 +1,8 @@
 ---
 license: apache-2.0
+pipeline_tag: image-to-image
+tags:
+- image-super-resolution
 ---
 # thera-edsr-plus