doc: add package doc
The package has no package comment for godoc to display, as seen at
https://godoc.org/go.googlesource.com/scratch.git or
https://godoc.org/goscratch.club. Adding a short description that gives
some context will help visitors to the godoc.
Fixes golang/go#27427
Change-Id: Ifdb993285955d6378c876849e0358efd316e1c5c
GitHub-Last-Rev: c89df9a12cb9e65d44c24c00c603e646e43b38e6
GitHub-Pull-Request: golang/scratch#29
Reviewed-on: https://go-review.googlesource.com/134222
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/doc.go b/doc.go
new file mode 100644
index 0000000..3bcd79d
--- /dev/null
+++ b/doc.go
@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package scratch exists mainly for people to learn how to use Gerrit
+// and contribute to Go.
+//
+// Read the README.md to access the tutorial.
+package scratch
