Add reviewers plugin to check pipeline

This adds the oauth plugin to the check pipeline.

Depends-On: https://gerrit-review.googlesource.com/273512
Change-Id: Ib0daaac6cbb22f679e0d7d8a1c8dbad654559c4c

zuul.d/projects.yaml

diff --git a/zuul.d/projects.yaml b/zuul.d/projects.yaml
index 977b1ee..402744a 100644
--- a/zuul.d/projects.yaml
+++ b/zuul.d/projects.yaml
@@ -91,3 +91,9 @@
     check:
       jobs:
         - gerrit-plugin-build
+
+- project:
+    name: plugins/reviewers
+    check:
+      jobs:
+        - gerrit-plugin-build