chore: vendor clipboard into go package

packages/tui/clipboard/tests/Makefile

@@ -0,0 +1,15 @@
+# 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>
+
+all: test
+
+test:
+	go test -v -count=1 -covermode=atomic ..
+
+test-docker:
+	docker build -t golang-design/x/clipboard ..
+	docker run --rm --name cb golang-design/x/clipboard
+	docker rmi golang-design/x/clipboard