Add jd_lists_unified.cs to default doclava templates.

Change-Id: Id5d6bc84f7c8bccbcb1d053db0b07850400a9dbc
diff --git a/res/assets/templates/jd_lists_unified.cs b/res/assets/templates/jd_lists_unified.cs
new file mode 100644
index 0000000..417a5c1
--- /dev/null
+++ b/res/assets/templates/jd_lists_unified.cs
@@ -0,0 +1 @@
+<?cs var:reference_tree ?>