doc: add README

Change-Id: Ia281ebc576c92d4a1ce79f5e08984ca5f00390f7
Reviewed-on: https://go-review.googlesource.com/14811
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/README b/README
new file mode 100644
index 0000000..2f02bee
--- /dev/null
+++ b/README
@@ -0,0 +1,7 @@
+This subrepository holds the source for the Go playground. https://play.golang.org/
+
+To submit changes to this repository, see http://golang.org/doc/contribute.html.
+
+To deploy a new sandbox server, use the gcloud tool:
+
+$ gcloud --project golang-org preview app deploy --set-default sandbox/app.yaml