Fix: REUSE for miniz.h, spng.c & display-drivers.md

miniz MIT: https://github.com/richgel999/miniz/blob/master/LICENSE
libspng BSD-2: https://github.com/randy408/libspng/blob/master/LICENSE

Signed-off-by: Peter M <[email protected]>

Author: petermm

docs/display-drivers.md

@@ -1,3 +1,8 @@
+<!--
+SPDX-License-Identifier: Apache-2.0
+SPDX-FileCopyrightText: AtomGL contributors
+-->
+
 # Display Drivers
 
 This document describes how to configure and use the various display drivers supported by AtomGL.

miniz.c

@@ -1,3 +1,6 @@
+/*
+SPDX-License-Identifier: MIT
+*/
 #include "miniz.h"
 /**************************************************************************
  *

miniz.h

@@ -1,3 +1,9 @@
+/*
+SPDX-License-Identifier: MIT
+SPDX-FileCopyrightText: 2013-2014 RAD Game Tools and Valve Software
+SPDX-FileCopyrightText: 2010-2014 Rich Geldreich and Tenacious Software LLC
+*/
+
 #define MINIZ_EXPORT
 /* miniz.c 2.2.0 - public domain deflate/inflate, zlib-subset, ZIP reading/writing/appending, PNG writing
    See "unlicense" statement at the end of this file.

spng.h

@@ -1,4 +1,7 @@
-/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+SPDX-License-Identifier: BSD-2-Clause
+SPDX-FileCopyrightText: libspng contributors (https://github.com/randy408/libspng/graphs/contributors)
+*/
 #ifndef SPNG_H
 #define SPNG_H