ao/pipewire: Add copyright header

Sometimes the most obvious things can be missed.

Reflects authorship described in the original commit.

* #7902
* Oschowa@fddb143
* #9587

audio/out/ao_pipewire.c

@@ -1,3 +1,24 @@
+/*
+ * PipeWire audio output driver.
+ * Copyright (C) 2021 Thomas Weißschuh <thomas@t-8ch.de>
+ * Copyright (C) 2021 Oschowa <oschowa@web.de>
+ * Copyright (C) 2020 Andreas Kempf <aakempf@gmail.com>
+ *
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
 #include <pipewire/pipewire.h>
 #include <spa/param/audio/format-utils.h>