Add REUSE ignore tags in Contributing guide

Author: flashcode

CONTRIBUTING.md

@@ -52,12 +52,16 @@ The copyright and license must be present in header, using [SPDX](https://spdx.d
 
 Example of header in a Python script:
 
+<!-- REUSE-IgnoreStart -->
+
 ```python
 # SPDX-FileCopyrightText: 2025 Your Name <[email protected]>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
 ```
 
+<!-- REUSE-IgnoreEnd -->
+
 ## Updating a script
 
 ### Contacting the author