Add License headers to cmake code

CMakeLists.txt

@@ -1,3 +1,9 @@
+# SPDX-FileCopyrightText: 2020-2021 Carl Schwan <carl@carlschwan.eu>
+# SPDX-FileCopyrightText: 2020-2021 Nicolas Fella <nicolas.fella@gmx.de>
+# SPDX-FileCopyrightText: 2020-2021 Tobias Fella <fella@posteo.de>
+# SPDX-FileCopyrightText: 2021 Adriaan de Groot <groot@kde.org>
+# SPDX-License-Identifier: BSD-2-Clause
+
 cmake_minimum_required(VERSION 3.1)
 
 project(NeoChat)

cmake/Findcmark.cmake

@@ -1,3 +1,6 @@
+# SPDX-FileCopyrightText: 2019 Black Hat <bhat@encom.eu.org>
+# SPDX-License-Identifier: GPL-3.0-only
+
 #
 # CMake module to search for the cmark library
 #

cmake/Flatpak.cmake

@@ -1,3 +1,6 @@
+# SPDX-FileCopyrightText: 2020 Carl Schwan <carl@carlschwan.eu>
+# SPDX-License-Identifier: BSD-2-Clause
+
 include(GNUInstallDirs)
 
 # Include FontConfig config which uses the Emoji One font from the

src/CMakeLists.txt

@@ -1,3 +1,8 @@
+# SPDX-FileCopyrightText: 2020-2021 Carl Schwan <carl@carlschwan.eu>
+# SPDX-FileCopyrightText: 2020-2021 Nicolas Fella <nicolas.fella@gmx.de>
+# SPDX-FileCopyrightText: 2020-2021 Tobias Fella <fella@posteo.de>
+# SPDX-License-Identifier: BSD-2-Clause
+
 add_executable(neochat
     accountlistmodel.cpp
     controller.cpp