Updated documentation procedure and added recommendation for contributors to...

Updated documentation procedure and added recommendation for contributors to add their copyright notice in the headers.

dco-cla/contributing-guidelines.md

@@ -21,7 +21,9 @@ further guidance on the handling of contributions You send Us.
      key.
 
  II. **If You are contributing documentation:** Please ensure to sign-off
-     Your commits with a GPG key.
+     Your commits with a GPG key. By signing-off your commits, You indicate
+      that You have read [these terms](./dco.md) and that You agree with
+      these.
 
 III. **If You are submitting code contributions (e.g. features,
      components):** please identify Yourself in one of the following
@@ -127,6 +129,11 @@ specifically refer to these obligations.
 We reserve the right to refuse Your contribution for non-compliance
 reasons or for not providing us with the required list of dependencies.
 
+We recommend that You include in the file headers of your code contributions the copyright notice acknowledging the ownership You have on the contribution: 
+
+Example: Copyright 2023 John Doe, Copyright 2023 European Maritime Safety Agency 
+
+
 **Signing** **of the CLA:** Please note that the CLA You sign for this
 project does not apply to other projects of the EC. If you are
 contributing to several projects, You need to send a signed CLA for each