fix discord hook bug (#2778)

Author: lunny

models/webhook_discord.go

@@ -1,3 +1,7 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
 package models
 
 import (

templates/org/settings/hook_new.tmpl

@@ -15,6 +15,8 @@
 							<img class="img-13" src="{{AppSubUrl}}/img/gogs.ico">
 						{{else if eq .HookType "slack"}}
 							<img class="img-13" src="{{AppSubUrl}}/img/slack.png">
+						{{else if eq .HookType "discord"}}
+							<img class="img-13" src="{{AppSubUrl}}/img/discord.png">
 						{{end}}
 					</div>
 				</h4>