Add copyright header and gitea-vet (#29)

Add copyright header

Co-authored-by: sillyguodong <[email protected]>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/29
Reviewed-by: Jason Song <[email protected]>
Reviewed-by: Zettat123 <[email protected]>
Co-authored-by: sillyguodong <[email protected]>
Co-committed-by: sillyguodong <[email protected]>

main.go

@@ -1,3 +1,6 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
 package main
 
 import (