endpoints: add Battlenet endpoints

OAuth APIs: https://develop.battle.net/documentation/battle-net/oauth-apis

Change-Id: I7c10f68c6ef0cb9b77cffa104e71a7198a599c89
GitHub-Last-Rev: e959643
GitHub-Pull-Request: #489
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/310249
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

Author: akaij

endpoints/endpoints.go

@@ -17,6 +17,12 @@ var Amazon = oauth2.Endpoint{
 	TokenURL: "https://api.amazon.com/auth/o2/token",
 }
 
+// Battlenet is the endpoint for Battlenet.
+var Battlenet = oauth2.Endpoint{
+	AuthURL: "https://battle.net/oauth/authorize",
+	TokenURL: "https://battle.net/oauth/token",
+}
+
 // Bitbucket is the endpoint for Bitbucket.
 var Bitbucket = oauth2.Endpoint{
 	AuthURL:  "https://bitbucket.org/site/oauth2/authorize",