Add a CI check ensuring the code has license headers (#6609)

* Introduce a job scanning and ensuring there are licenses

* Showcase a red test

* Add missing licenses

* Cleanup

* Extend the check

* Add missing licenses

* CI trigger

polkadot/node/network/protocol/src/reputation.rs

@@ -1,3 +1,19 @@
+// Copyright 2017-2023 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
 pub use sc_network::ReputationChange;
 
 /// Unified annoyance cost and good behavior benefits.