wiki: add nav.yaml

This will be used for the new sidebars.

Change-Id: I425f38af4497e6a2f7b8e3605dbbb84c08f80e4c
Reviewed-on: https://go-review.googlesource.com/c/wiki/+/550955
Reviewed-by: Russ Cox <rsc@golang.org>
Commit-Queue: Russ Cox <rsc@golang.org>
diff --git a/nav.yaml b/nav.yaml
new file mode 100644
index 0000000..86d593f
--- /dev/null
+++ b/nav.yaml
@@ -0,0 +1,3 @@
+name: Go Wiki
+subs:
+- name: Other Pages