kakao: Add new endpoint of Kakao

Change-Id: I1f95cb91018f96f74c1079128cbbd5ebe553c58e
Reviewed-on: https://go-review.googlesource.com/114856
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

kakao/kakao.go

@@ -0,0 +1,16 @@
+// 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 kakao provides constants for using OAuth2 to access Kakao.
+package kakao // import "golang.org/x/oauth2/kakao"
+
+import (
+	"golang.org/x/oauth2"
+)
+
+// Endpoint is Kakao's OAuth 2.0 endpoint.
+var Endpoint = oauth2.Endpoint{
+	AuthURL:  "https://kauth.kakao.com/oauth/authorize",
+	TokenURL: "https://kauth.kakao.com/oauth/token",
+}