Update docs/faq.md: add a copyright header

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/faq.md

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+SPDX-FileCopyrightText: 2021 - 2022 MDAD project contributors
+SPDX-FileCopyrightText: 2021 - 2024 Slavi Pantaleev
+SPDX-FileCopyrightText: 2022 Julian-Samuel Gebühr
+SPDX-FileCopyrightText: 2022 László Várady
+SPDX-FileCopyrightText: 2024 - 2025 Suguru Hirahara
+SPDX-FileCopyrightText: 2024 Nikita Chernyi
+SPDX-FileCopyrightText: 2024 Uğur İLTER
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+SPDX-License-Identifier: AGPL-3.0-or-later
+-->
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 # Frequently Asked Questions
 
 This documentation page tries to answer various Frequently Asked Questions about all things [Matrix](https://matrix.org/), with a focus on this [Ansible](https://www.ansible.com/) playbook ([What is Ansible? How does it work?](#what-is-ansible-how-does-it-work)).