pkgsite-metrics: add codereview.cfg

For golang/go#9273.

Change-Id: I27e8c4acbaa582386e0863e674e973771d13e847
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/740161
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Sean Liao <sean@liao.dev>
diff --git a/codereview.cfg b/codereview.cfg
new file mode 100644
index 0000000..3f8b14b
--- /dev/null
+++ b/codereview.cfg
@@ -0,0 +1 @@
+issuerepo: golang/go