chore: vendor clipboard into go package

packages/tui/clipboard/export_test.go

@@ -0,0 +1,14 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+package clipboard
+
+// for debugging errors
+var (
+	Debug          = debug
+	ErrUnavailable = errUnavailable
+	ErrCgoDisabled = errNoCgo
+)