Add titles to Bazel documentation pages.

Fixes #790

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MOS_MIGRATED_REVID=112563137
diff --git a/site/docs/tutorial/backend-server.md b/site/docs/tutorial/backend-server.md
index fc85cd6..073ffbc 100644
--- a/site/docs/tutorial/backend-server.md
+++ b/site/docs/tutorial/backend-server.md
@@ -1,3 +1,8 @@
+---
+layout: documentation
+title: Tutorial - Build the Backend Server
+---
+
 # Tutorial - Build the Backend Server
 
 The backend server is a simple web application that runs on Google App Engine