Add readonly plugin checker

Change-Id: Ibeecba0cc8d1e4be27eab33045b3d77409b8ae81
diff --git a/checkers.yaml b/checkers.yaml
index ad2d132..edce824 100644
--- a/checkers.yaml
+++ b/checkers.yaml
@@ -176,6 +176,11 @@
     name: "Zuul Check Pipeline"
     description: "Run Zuul jobs on new patchsets"
 
+  - uuid: "zuul-check:plugins_readonly"
+    repository: "plugins/readonly"
+    name: "Zuul Check Pipeline"
+    description: "Run Zuul jobs on new patchsets"
+
   - uuid: "zuul-check:plugins_reviewers"
     repository: "plugins/reviewers"
     name: "Zuul Check Pipeline"
diff --git a/zuul/main.yaml b/zuul/main.yaml
index a2a13d2..66944be 100644
--- a/zuul/main.yaml
+++ b/zuul/main.yaml
@@ -48,5 +48,6 @@
           - plugins/project-group-structure
           - plugins/quota
           - plugins/rate-limiter
+          - plugins/readonly
           - plugins/reviewers
           - plugins/saml