Add GET requests to webhook (#6771)

* Add GET requests to webhook

* make fmt

* Handle invalid http method on webhook

* Uppercase http method in webhook

* Rename v85.go to v86.go

* make fmt

models/migrations/v86.go

@@ -0,0 +1,17 @@
+// Copyright 2019 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 migrations
+
+import (
+	"github.com/go-xorm/xorm"
+)
+
+func addHTTPMethodToWebhook(x *xorm.Engine) error {
+	type Webhook struct {
+		HTTPMethod string `xorm:"http_method DEFAULT 'POST'"`
+	}
+
+	return x.Sync2(new(Webhook))
+}