Add image-diff plugin

Depends-On: https://gerrit-review.googlesource.com/c/zuul/ops/+/379098
Change-Id: Ie470ded13e133949709f2aae9212e96825d6c33b
diff --git a/zuul.d/projects.yaml b/zuul.d/projects.yaml
index 9b59639..b35aa05 100644
--- a/zuul.d/projects.yaml
+++ b/zuul.d/projects.yaml
@@ -179,6 +179,11 @@
       - non-core-plugin
 
 - project:
+    name: plugins/image-diff
+    templates:
+      - non-core-plugin
+
+- project:
     name: plugins/its-base
     templates:
       - non-core-plugin